http://links.f5.com/aAGhYQ
Your cell phone is the 2nd factor.
Regarding OAuth, here are some links to get you started.
http://links.f5.com/cmd7oJ
Twitter implemented it, but they asked developers not to put their keys in their application (and then allowed some important clients to exactly that)
http://links.f5.com/c3WLFN
