Thanks clubsofsteel, just so that everybody understands, the coins are held in a type of multi-sig address so that it needs one party to agree to release the funds to the other party.
 Before you start the contract you both agree on an arbitrator - I've used fuzzyBear to arbitrate these bets so that if both parties disagree they can start a dispute and call in the arbitrator.
 Anyone can become an arbitrator just by ticking a box in their profile.
 
 You can have bets with friends or strangers as long as you can both agree on someone you can trust to arbitrate. The idea is to make escrow transactions really quick and simple.

 It should be really useful for currency exchange too.