Abandoned project on bill splitting.
Natwest et al's send money via SMS is a better solution that I cannot replicate. Also facebook is doing it, that'd make it even easier.
Then Alice and Bob will see this in their inbox. They can then pay the bill in 2 clicks.
This repo includes the first itertion in native Android, then a second iteration in PhoneGap.
Before you start, you should run git submodule update --init --recursive to fetch all the submodules