We're both very big Billmonk fans, but unfortunately the application hasn't seen very much improvement since it was acquired a few years ago. Splitterbug helps you solve the same problem using some very cool tech that Billmonk didn't have access to (native iPhone apps/Android/Facebook graph/etc).

Our primary focus right now is building an app solves the problem of splitting bills and tracking debts. We've got a few ideas about monetization, but if we can't build a useful app first, that discussion is moot.