I've been tinkering with the idea for a few months now. Initially a normal coindice site was on the table but after reviewing the aspects (risks, trust relation, etc) I concluded it wouldn't be viable.

The principal for users needs be simple with a low barrier; People can send an X amount from their local wallet to the online address with the according win ratio and get paid or not. This will be verifiable trough the blockchain by combining the TXID and secret hash (provably fair). A small issue here is the long confirmation time so I'm keeping an eye on InstantTX.  

Edit; to give you an idea, look at the workings of bitzillions