[DLarsen]

Pretty neat. I'm also working on a side project in the same vein. The key to improving spending behavior in my own household has been to focus on and evaluate decisions. http://www.spendlight.com/

My approach is a bit broader in that I find it useful to record both the good and bad decisions with a view toward improvement.

I also prompt users for a bit of self-evaluation. When you goof, you are asked something like "What could you have done without in order to stay within your limits?" When you do well, you are asked something like "What was the key to making wise choices today?"

I'm not a big fan of the input mechanism. It's novel and fun, but I'd bet that the fun wears out quickly.