this is an awesome idea for mobile phones. It does the job of many apps in a single app and the interface beats them all. It couldn't be any easier to enter a transaction. You enter just the name of the book that you are borrowing or lending - and everything else is already filled in for you. If you are entering a money transaction then all you have to enter is a description (lunch, movie ticket etc.) and an amount that you paid for your friend (or your friend paid for you). Entering a transaction cannot get any easier than that. You have to write a lot more even in your notebook. And from that simple entry, this app is able to calculate and tell you exactly how much money you are going to get right on the app icon - I think that's the coolest thing. You don't even need to launch the app to know how much money you need to get from your friends.