This is nifty, in the same way that the "don't break the chain" ideas are nifty (I like this kind of GTD idea, and making it social is cooler). Start thinking about the business case for this idea, though. I don't mean you have to know how to make money today...I'm just wondering how big you visualize the market for this product being. Whether it's a feature or a product you want something that appeals to a very large swath of people (or a small swath with disposable income to spend on what you're providing).