The BCCAPI (Bitcoin Client API) is a java library designed for making secure light-weight bitcoin clients. The BCCAPI connects to a server that holds the block chain, and which tracks the client’s wallet balance. The server only has knowledge of the clients public keys, and is in no position to spend funds owned by the client’s wallet.
Features include: Deterministic private keys Zero backup Low bandwidth Low CPU usage Server cannot spend your coins Open source Free service, running on donations
Simply put the API is designed for making it easy to create light-weight secure Bitcoin wallets for handheld devices.
The sources include a very simple console based client, that shows how to use it. I am not an Android developer, and my hope is that the community will pick this up and make some great apps.
More information and the source: http://code.google.com/p/bccapi/wiki/WhatIsTheBCCAPI
Support the BCCAPI: 143SikKpjzwhBy5Z7Qg5knu5nKXWExSqQi