Facebook already knows pretty much everything about you. Heck, the company’s even admitted to playing with some people’s emotions just to see what might happen. One bit of data the social networking giant still doesn’t know is how much money you spend, but it looks like the company is working on an interesting new financial management app that could make you feel really good (or really bad) about how much you’re spending compared to your friends and peers.

A recent Facebook patent spotted by Bank Innovation describes how the company could use its social graph to compare your financial transactions to other people in the same age bracket who also share your interests. One image shows a rudimentary user interface for the app with three graphs breaking down your own spending habits, your group average and how you compare to everyone else. The app could also offer suggestions based on your peers’ spending habits.

It’s an interesting idea, though we’re not quite sure what other things we “Like,” such as our taste in music, movies and sports teams has to do with our spending habits. Facebook is definitely in the perfect position to launch this kind of service, which could really help some people curb their spending habits. The tough part will be convincing both banks and regular people to share their financial information with the social network, which doesn’t exactly have the best record when it comes to protecting user privacy.

Of course this is just a patent, and for now it’s still up for approval with the U.S. patent office. Either way Facebook’s definitely gearing up for a push into the e-commerce market, and we’re curious to see how the company’s payment plans play out.