My video camera streams UDP via WiFi to my Android phone.

I'd like to re-stream from Android, so I need a library for the application layer RTSP, for UDP.

My question is: is there such a library anywhere out there (free or not) already available?

If not, about how much difficult would be to write one? (I understand that for .NET there is such a library so the logic could be borrowed for writing code in JAVA or NDK)

Thanks.