Splitwise is an advanced, but easy to use app that keeps the basic accounting for group of persons. Split expenses and track how much money you must receive back from each participant.
Is available as online service or mobile application, easily add events, participants and how money you must receive. Each member of group/event will se the list and they will remember easily how much and from what event they owe money.
Splitwise may be considered a good BillMonk alternative, users can send money online via Paypal secure service or record a cash payment.
Easily add friends in your interface, view upcoming bills and more.