“S Diary” is a mini social life costs/rewards monitor.  Apart from properties most event management app record, “S Diary” also records your spend and satisfaction rate for an event, and associate them with your friends, coworkers, and etc. involved in this event.  It will calculate the average spends and rates for each person recorded in app and generate a list. You can choose to view the list by average spends (high to low) or average rates (high to low).   While the relationship between costs and rewards is complicated to measure in real life, you would find this app useful for tracking social spends and for fun as well.