Sportsbetting should be your #1 priority. It's a massive market where the standard juice is 5%. Make an easy to use betting platform with smaller juice and there would be no reason for people to use traditional sites.
it already exists using the counterparty protocol - countersports pre announced on bitcointalk - expect what happens when it is launched.
twin is basically right - also the configuration of cha protcol is concentrated on games against the house - counterparty is for peer to peer (gambling)