Multipurpose gadgets — from the dubious devices hawked on late-night television to reliable standbys like food processors — capture our fancy because they promise to save space, time, and money. The iPhone, Android, and BlackBerry are no exception. Aptly dubbed “smartphones,” they don’t just make calls — they’re also highly portable, powerful computers that can perform a seemingly infinite variety of tasks, thanks to operating systems that run programs called applications, or “apps.”

Hundreds of thousands of smartphone apps are already available for downloading, including some 250,000 for the iPhone, 80,000 for the Android, and 12,000 for the BlackBerry. And more are being created all the time. Over a thousand of these apps are aimed at improving health and fitness. Some, like calorie and exercise logs, are sophisticated alternatives to pencil and paper, providing a convenient format for entering, storing, and charting personal data. Others, like MyOBGYN and Medscape, provide state-of-the-art medical information or the latest medical news. And an increasing number of apps are taking advantage of built-in smartphone features — such as microphones, motion sensors, and global-positioning systems — that turn smartphones into pedometers, sleep monitors, and medical-assist devices.

Evaluating apps

Because the field is enormous, ever-changing, and largely unregulated, app shopping can be something of a challenge. Many apps are free and, increasingly, supported by advertising. Those that have price tags may offer a free “lite” version or a test run online. Like other products sold on the Internet, most apps are rated by consumers according to a one- to five-star system, though often the number of reviewers is too low to be meaningful.

The best way to start might be to download some free apps to your smartphone, delete the ones that don’t live up to your expectations, and consider spending a dollar or two to upgrade those you like — or simply buy the well-rated ones that seem especially appropriate for your needs. You can view the offerings — and how users have rated them — at Apple’s App Store, Google’s Android Market, or BlackBerry’s App World. Links to all three are available at www.health.harvard.edu/womenextra. The following are among the most widely downloaded and highly rated health and wellness apps.

For women only

The app stores don’t classify apps by gender, but you can find several programs that specifically address women’s health issues. Here are a few.

Whether you are trying to get pregnant, are in the midst of perimenopause, or find that your period often takes you by surprise, Period Tracker Lite or iPeriod (for iPhone, free), Free Menstrual Calendar (for Android, free), or Period Calendar Deluxe (for BlackBerry, $3.99) may be for you. These apps aren’t substitutes for medical tests, but they can help you collect data to take to your doctor. You start by entering the start and duration of your periods, your weight, and your body temperature. The apps then calculate when you can expect your next period and what days you’ll be fertile. If you have premenstrual syndrome (PMS), it can be helpful to see your symptoms, mood, and menstrual flow displayed on a calendar.

Kegels — the exercises that strengthen the pelvic floor muscle to prevent urine from leaking — are well suited for smartphone coaching because you can do them almost anywhere you can take your phone. For women who have difficulty performing rhythmic pelvic-floor contractions, KegelTopia (for iPhone, $1.99) offers instructions on how to isolate your pubococcygeus muscles, the voice of a yoga instructor to guide you through three different exercise routines, and a log to track your sessions. Other options include — for the Android — Kegel Muscle Exerciser (free) and Kegel Exercises Counter ($3.99), and for the BlackBerry, there’s Kegel Timer (for the BlackBerry, $2.99). All are essentially electronic metronomes; they will help you stay on track if you know how to do the contractions, but they don’t offer much else.

MyOBGYN (for iPhone, 99 cents; a lite version is also available for free) is an easily browsable compendium of reproductive health information that’s divided into two categories — pregnancy and nonpregnancy. Written by specialists in obstetrics and gynecology, it’s a concise and trustworthy guide to almost anything you’d want to know about your breasts and reproductive system, including medical conditions and the drugs and procedures used to treat them.

Weight control and fitness

Food diaries and supportive communities are proven factors in successful weight control; Lose It! (for iPhone, free) offers both. You enter your height, weight, age, gender, and target weight, and the app calculates your daily calorie allotment. As you go through the day, you log in every morsel you put into your mouth and each minute of physical activity. The app draws from a seemingly bottomless database of foods and physical activities to keep a running tab of the calories you’ve consumed and expended and the number remaining in the day’s allotment. It also computes your intake in terms of calories, carbs, protein, saturated and unsaturated fats, and sodium. Because the required discipline can be tedious, the app facilitates a little self-nagging — you can set up e-mail notes to yourself reminding you to fill out the log. You can also register on the Lose It! Web site to get support from others who’ve had success in losing weight.

Calorie Counter by FatSecret (for iPhone, Android, and BlackBerry, free) is similar but less intuitive to use and does less of the math for you.

iTreadmill (for iPhone, 99 cents), CardioTrainer (for Android, free), and Endomondo Sports Tracker (for Android and BlackBerry, free) use the phones’ GPS systems to turn them into pedometers and navigators.

Medical information apps

The following apps put a trove of medical information at your fingertips. Some provide professional-quality information; others, breaking news.

Read what hundreds of thousands of medical professionals are reading with the Medscape app (for iPhone and BlackBerry, free; an Android version is in the works). The basic medical information is organized into three categories — drugs and herbals, diseases and conditions, and procedures and protocols. Breaking news from medical journals appears in a balloon on the home page. This app provides more information than you’ll probably ever need, but you don’t have to download it all on your phone; you can save 20 minutes by skipping the 3,000 clinical summary articles.

MedPage Today Mobile (for iPhone and Android, free) concentrates on breaking medical news that’s likely to receive wide press coverage. Because it’s directed at physicians and overseen by medical professionals, the coverage is more detailed — and probably more reliable — than you’ll find in the general media.

Public health apps

If news reports have raised your awareness of foodborne diseases and potential pandemics — and perhaps your anxiety level, too — two apps from HealthMap can provide a reality check. Produced in collaboration with medical professionals at major medical centers, the apps not only disseminate but also gather information about public health issues.

MedWatcher (for iPhone, free) lets you keep abreast of drug recalls through almost daily bulletins from the FDA. There’s an option for receiving immediate alerts on drugs that you and your family are taking. MedWatcher also includes a user-friendly form for recording adverse reactions, which is then sent directly to the FDA.

Outbreaks Near Me (for iPhone and Android, free) was released just in time for the flu season. It uses the phones’ GPS software to pinpoint your location; then it scans several sources — including the Centers for Disease Control and Prevention and the popular news media — to compile a list of recent outbreaks in your area. You can also sign up to receive e-mail alerts on particular topics, such as chickenpox or salmonella. Like MedWatcher, Outbreaks Near Me has a form for reporting any infectious diseases you might encounter.

Health aids

If you have trouble remembering when to take your medication — or whether you took it at all — you can buy an alarm-equipped pillbox, or you can choose from several free or inexpensive smartphone apps that offer most of the same functions. Pill Tracker (for iPhone, free), Pillbox Alert (for Android, $1.99), and MediRemind (for BlackBerry, $2.99) will let you know when to take your medicine. Pill Tracker and Pillbox Alert fire off what look like text messages (but you won’t be charged a texting fee) when it’s pill time. They also prompt you to note whether you’ve taken the medication, by entering that information into a log. MediRemind stores drug, clinician, and insurance information. (One unresolved issue with all these apps: you still need to remember to have your pills handy when the reminder to take them comes!)

When you find yourself under stress, Breathing Zone (for iPhone, $1.99) can help unruffle your feathers. This app employs the phone’s microphone to assess your breathing, then establishes a realistically reduced “target rate.” You can choose an audio accompaniment and set the length of your relaxation session. You then breathe in and out in sync with an image that pulsates at a gradually slower pace. Breath Pacer Lite (for Android, free) offers the same features, but the visual experience is less hypnotic. BlackBerry’s paced-breathing program, MyCalmBeat (99 cents), offers charts, graphs, and tracking but no visual or audio aids.

Sleep Cycle alarm clock (for iPhone, 99 cents) and Smart Alarm Clock (for Android, free) can help you wake up feeling refreshed by identifying a time when you’ll be least likely to interrupt restful “deep sleep.” You position your phone on the mattress and allow it to “observe” you for a few nights as you sleep. The phone’s accelerometer (motion sensor) registers your movements, determines the deepest and shallowest points in your sleep cycle, and sets the alarm to the point (within a 30-minute wake-up window you establish) at which you’re least likely to be in deep sleep. One caveat: the apps won’t work with pressure-sensitive foam mattresses.

iDown (for iPhone, $2.99) can give you some peace of mind if you worry about falling and lying undiscovered for hours. The app relies on the phone’s accelerometer to detect a sudden shift from vertical to horizontal and the phone’s GPS to track your whereabouts. You need to wear it upright in a pocket or on a belt to be sure the app is running. If you fall, the app will e-mail an alert giving your phone number and location to two contacts you’ve designated. If you decide you don’t need help, you have a few seconds (you can determine how long) to reset the app. A similar app, iFall, is expected for the Android soon.

The appscape of the future

The FDA has been keeping a watchful eye on smartphone apps to determine when they cross the line from record-keepers to medical devices, which require FDA approval. In July 2010, the FDA ruled that the WellDoc DiabetesManager System should be marketed as a medical device because it not only logs glucose levels but also gives medical advice based on the results. It’s slated to be available in 2011; apps for asthma, cardiovascular disease, and cancer are scheduled to follow.

And that’s just the beginning. As these phones and their apps get smarter and smarter, they’ll become more integral to maintaining good health and managing disease. We’ll keep you in the loop.

Incoming search terms:

• Period Tracker Lite or iPeriod (for iPhone free) Free Menstrual Calendar (for Android free) or Period Calendar Deluxe