Basically a specialized bitcoind that the buyer sends a payment to and when everything is good, the buyer sends a special "all clear" message to that server that then knows to "release" what it has to whoever it's suppose to go to.
Programming wise, should be possible with direct IP payments for example, where the "From" and "Comment" fields can be used to "reserve" the BTC until later.
One could send a transaction and in the comment field put something like "Escrow= Amount=1000.00 Release=".
When the buyer gets the stuff and he/she is happy, they send a 0.01 payment to the same escrow server "Escrow= Amount=1000.00 Release=" and the server sees the match, knows it's ok to send payment to that address, for that amount, etc.
Very doable from a programming standpoint.
kind of, the point of this system is that you can leverage the network for escrow transactions so long as everything goes to plan, thereby ensuring a low cost. in instances of dispute, you will pay a third party.