I am slowly working on a bitcoin-android client, but as i have so many projects on the go right now it might take me a while.

I don't really care about the bounty so much as seeing another implementation, so here is what I have to date, which will hopefully help other people writing other implementations.

https://github.com/dirtyfilthy/bitcoin-wallet

This code is unfinished, largely untested and probably a bit shit. Java is not my native tongue so I probably use incorrect idioms all over the show. It does contain however:

Base58 encoding/decoding
Keypair generation and signing
Serialisation routines
The beginnings of a blockchain class
A bouncy-castle provider refactored to not interfere with androids bouncy castle
+ other bits and pieces

Though there is no licence file consider this code released under the GPL