lock-in

Google Play services is an Android library whose goal is to provide: OAuth 2.0 authentication Google+ sign-in Google+ +1 button various other goodies If I were to use it (for instance because I want Google+ sign-in), what would happen to users whose device does not have Google Play? (Nook, Cyanogenmod, China Mobile, old devices, maybe Huawei? , etc) QUESTION: Will my app become incompatible with such devices? Will it be displayed as compatible but then crash, or not work? Is there a best practice to keep this in mind when using Google Play services? GooglePlayServicesUtil

Are there any guidelines to writing Google App Engine Python code that would work without Google's infrastructure on other platforms? Is there any known attempt to create an open source framework which can run applications designed for Google App Engine on other platforms? Edit: To clarify, the question really is: If I develop an application on Google App Engine now, will I be able to migrate to another platform later, or is it a lock in? There's a number of components required to make an app fully portable: The runtime environment itself. This can be ported relatively simply, by setting up a