Android users are just going to have accept the pain of constant phone-homes. The only secure Android app is an always-connected Android app.
This is, in large part, due to Google's refusal to lock-down the installation, like Apple has. On IOS you have to jailbreak the phone. On Android you can load any APK on a stock, factory install.
Keep some/most/all your content on the server; deliver it in chunks; validate the license/session on each call.
