One of the first health apps built with Apple's ResearchKit platform is now available to download outside the US. MyHeart Counts, which was first announced at Apple's "Spring Forward" event in March, has been opened up to iPhone users in the UK and Hong Kong for the first time. Once you've opted in, you'll be asked every few months to take part in a weeklong test, which includes seven days of activity monitoring, a 6-minute walk and a submission of personal risk-factor information. Stanford University will offer a review of your heart's health in return, as well as some advice for improving general wellness, but the idea here is to make it as easy as possible to become a volunteer. ResearchKit was, after all, invented to help scientists and medical professionals conduct large-scale studies. There are over one billion iOS devices in the world, so if even a fraction of those take some time to use the app, that's a trove of new information that will benefit medical research.