Hi Rich,
Because there are different models of Nexus 7 and other tablets with varying technical specifications, the Play store doesn't allow us to give straight approval to the model as being compatible with our app. However, the Striiv app should theoretically work on your devices as long as the screen is large enough, running on Android 4.3 or newer, with Bluetooth Low Energy, or Bluetooth 4.0.
If you're not able to download our app straight from the Play store, we can offer you directions on how to sideload the app onto your devices. Let me know if you're interested in that!
Rich Stylinski