Run IOS apps on Android http://www.greenbot.com/article/2155800/meet-one-of-the-developers-aiming-to-bring-peace-to-ios-and-android-users-everywhere.html
We have the internet, it can be very unproprietary. :P
Otherwise, there is almost always going to be a difference some where. Though I agree having platform limits is a problem. One of the reasons I've stuck to Windows. Even Apple OS has less compatibility over the ages than Windows has managed to squeeze through.