My Scientific American column this month is a page-long gasp of amazement at the potential of ResearchKit, Apple's new open-source tool kit for writing medical research apps. It has the potential to turn tiny, inefficient, limited medical studies into large, immediate, international ones.

A handful of institutions introduced five ResearchKit apps when the initiative launched this April. (Apple, which does not receive the collected data, collaborated on creating each of these free apps.) They're worth a closer look, if only because they're meant to be models for future ResearchKit studies.

Asthma Health (Icahn School of Medicine at Mount Sinai) for asthma sufferers: This six-month study will amass a mass of data about asthma and its triggers. (You must be an asthma sufferer to participate.) Each day you're asked three or four questions about how you feel and what asthma-related symptoms you've experienced; meanwhile, the app checks to see where you've been (using the phone's GPS). With that information it can correlate environmental factors such as heat index, pollen count, pollution level and weather to the onset of asthma attacks. The goal is to begin to parse more detailed data—about medicines, causes and effects—enough to begin to make personalizedasthma-care recommendations, rather than using the one-size-fits-all approach we use now.

GlucoSuccess (Massachusetts General Hospital) for type 2 diabetics and prediabetics: You enter your finger-stick glucose readings (the app can remind you at the appropriate time of day, too) and log the food you eat (using the free Lose It app). The app tracks your physical activity automatically from your phone's sensors. The researchers collect your data (anonymously, as with all of these apps) but the app also uses graphs and written blurbs to tell you how your diet and physical activity affect your blood glucose levels.

mPower (Sage Bionetworks, a nonprofit research institute in Seattle) for Parkinson's disease patients and healthy participants: Each day the app asks you to perform an activity. One asks you to say "ahhh" into the microphone for as long as you can on a single breath. One asks you to tap the screen alternately with two fingers as fast as you can. A third tracks your short-term memory by testing to see if you can remember a pattern of flowers lighting up. Over time the study is designed to reveal why Parkinson's symptoms differ by individual and how the symptoms and side effects vary over time.

MyHeart Counts (Stanford University School of Medicine) for heart disease and healthy controls: This study examines relationships between activity, motivation, risk factors and heart health. The app tracks your activity for a week, either from the phone's motion sensors or wearable devices compatible with HealthKit, Apple's central health app tool. Four times a year the app asks you to take a six-minute walking test. In time the app begins issuing motivational prompts, in an effort to inspire you to move more—and, of course, it tracks the results.

Share the Journey (Sage Bionetworks) for breast cancer, but all women are invited to join: This primarily survey-based app asks you questions about your current health and your medical history. The app (if you choose) also collects data about your physical activity. The study is intended to ferret out what causes symptom variations after breast cancer treatment.