OATH: yesterday, today, and tomorrow

Google's second-factor auth stuff is TOTP, so as well as the Android app, you can write a client for whatever device you choose to use. Google don't need to care what you use, the open standard lets you use whatever you want and just feed it the provided seed.

See the Google Authenticator:
http://code.google.com/p/google-authenticator/
which has an Apache License 2.0.