Pharmaceutical giant GlaxoSmithKline (GSK) has partnered with Apple on a new clinical study on rheumatoid arthritis. The study relies on an iPhone app to collect data about arthritic symptoms from users as they go about their daily lives. That sounds great at first glance, but how well will it protect your privacy?

The app was built by the London-based GSK using Apple’s ResearchKit, an open source software framework to transform your iPhone into a handy diagnostic tool for clinical studies. Launched last year, ResearchKit is designed to make it easier for medical researchers to access data about millions of potential subjects. As Lifehacker’s Alan Henry wrote at the time, “The platform aims to give anyone with an iOS device the opportunity to participate in medical research, join programs that can help them track their symptoms, or share information with their doctors.”

So far there are just a handful of ResearchKit apps tied to clinical studies, but the GSK partnership is the first time Apple has joined forces with a major drug company. The Patient Rheumatoid Arthritis Data from the Real World (PARADE) study will use its app to track the mobility of over 300 participants suffering from rheumatoid arthritis, including information on their level of joint pain, fatigue, and changing moods. No drugs are being tested. Rather, the app guides users through a simple wrist exercise, with the iPhone’s built-in sensors recording data from that motion. That data may help Glaxo design better clinical trials in the future.

There are plenty of potential benefits to using the ResearchKit platform. It’s a huge boon to recruiting viable participants for medical studies—which can take months or years, depending on the study—and it’s cost effective, potentially saving millions of dollars. “Certainly you’ve also taken out the site costs, and the costs of having nurses and physicians explaining the studies to them and recording information,” Rob DiCicco, head of Glaxo’s clinical innovation and digital platforms group, told Bloomberg News.

Read more: Gizmodo