Quote from: optimator on February 12, 2014, 10:54:18 PM

Quote from: yogi on February 12, 2014, 10:49:04 PM

I'm interested in tracking sent transactions, not received.

Just to be clear (Sorry if this is obvious...) a sent transaction uses both inputs and outputs to create the transaction. If you want to track the sent transaction you need to track the TxIns and TxOuts.

See - https://en.bitcoin.it/wiki/Transactions

By sending I mean I'm the creator of the transaction.

Costamonger has posted a workable solution, but this still seems a little convoluted.

Quote from: coastermonger on February 13, 2014, 04:07:02 AM

1.) When a customer withdraws bitcoin from your service, include an extra output in the transaction to spend a portion of your own BTC back to a new address you control.
2.) Track the presence of that output at your new address. (Through a callback for instance)
3.) Did the bitcoin arrive?

If yes, then congratulations, you can be sure that the funds involved were delivered
If no, then neither your funds or the customers withdrawal were successfully sent out to begin with.

If for whatever reason an attacker tried to manually spend or fake-double spend bitcoin back to your new address as a "trick," all they've accomplished is an action that forces your system to mark their withdrawal as successful.