The app highlights trends in blood-pressure readings and detects when people forget to take their measurements, reminding them with an automated phone call. Giving patients self-monitoring tools makes them aware of their health stats on a daily basis, rather than just in the week before a doctor's appointment, says Cafazzo. This is especially relevant for hypertension, which doesn't usually have detectable symptoms.

A second project focused on adolescents with diabetes, a challenging population for doctors because teens are transitioning from being cared for by their parents to being responsible for their own care. Researchers worked with Apple to create an app that is compatible with a blood-sugar monitor. The app reminds users to check their blood sugar and rewards users with iTunes certificates for healthy behavior. If it detects a string of low measurements, it will ask users what they think caused the trend. Teens who used the app checked their blood sugar twice as often as those who didn't.

Cafazzo hopes self-monitoring tools like these will be instrumental in changing how chronic conditions, such as diabetes and hypertension, are managed. These conditions represent a huge financial burden on health-care systems. "Primary care isn't the best place for chronic disease management," says Cafazzo. "It should go back to nurses and the patients themselves."

For both apps, researchers won approval from Health Canada (similar to the U.S. Food and Drug Administration) to run the clinical trials. As smart-phone apps become increasingly sophisticated, incorporating external sensors and intelligence to make recommendations to users, this type of approval will become more and more important. Cafazzo says they spent more money running the clinical trial than on developing the technology.

In July, the FDA announced its intentions to regulate smart-phone apps that are used as an accessory to a medical device already regulated by the FDA, or that use attachments, sensors, or other devices to transform the phone into a medical device.

Cafazzo's team plans to create a similar app for kids with asthma. He also hopes to collaborate with a company to commercialize the two existing apps. A limited version of the diabetes-monitoring app is currently available in the Apple app store; it doesn't include automated blood-sugar monitoring but encourages users to test themselves regularly.