Thanks for the advice.
Satoshi roulette is cool. I considered this too but don't have the coin needed to payout when someone wins.
To start I would limit the wheel to one btc bets.

I was planning on running my own bitcoind service on a server.
The reason why I want to return the money after some time (and limit the deposit amount) is to avoid getting hacked. In the case I would get hacked the amount stolen would be far less I think. However the suggestion of providing an alternative withdraw address is something I would add to the app.

But I'm not sure a bitcoin wheel of fortune will be a great success. It isn't the most exciting game but does provide a quick gamble 
I would prefer to develop something a bit more exciting but something like a full-on poker game would be a bit too time consuming for a side project.
If I can't produce a better idea by the end of the month, I'll probably start this.
I'm eager to do something bitcoin