At the moment, PT.Transact Classic is only available on iOS devices (iPhone, iPad and iPod Touch).
Why is this?
The short answer is, because we had to start somewhere :-)
The longer answer is that in an ideal world, we'd have the resources and money to put our efforts into building both iOS and Android versions of the app at the same time. But we're a small, dedicated team building what we believe is becoming the most useful, convenient and efficient client payments app for personal trainers in the world, and we only have the resources to focus on one platform at a time. So far, this has been iOS. We aren't deliberately ignoring Android or leaving Android users out in the cold. The good news is that we've started preliminary work on PT.Transact for Android. We aren't in a position to announce timeframes yet as this is still being sorted out. But rest assured that we'll have something to announce for Android users soon.