The popular bitcoin betting game Satoshi Dice sends back payments very fast, they don't wait for confirmations. The user sends money to Satoshi Dice and gets back winnings a couple of seconds later. Here's a quote from their site:
The SatoshiDice Bitcoin game operates with zero confirmations [...] This is safe because it always builds the answering transaction with the output of your bet transaction. This means a blockchain that does not contain your bet cannot contain the site's answer.
I think I understand the theory behind this: Satoshi Dice always sends back coins from your own bet. So if your bet doesn't get confirmed then your winnings also won't get confirmed.
What I don't understand is how I could technically create these kind of transactions. Using bitcoind, how could one build these transactions?
Thanks for your suggestions.