Startup Idea : bet on the go!

A mobile gaming app majorly for bet lovers. To include mainly car race and a few others. So that one can be able to challenge another player from anywhere in the world to a bet with a stake amount. A payment mode would be integrated from where members can fund their betting acount. So you can search who's online and challenge them. Games can be replayed if internet disrupts and such rules will be in place. Free challenges can also be available. Not sure if something exactly already exist anyway, even so, I wish to realise this. I'll like to hear from members.