How can I check a 0-confirmation Bitcoin transaction without having the private key in my wallet?

Question

I am programming a site that accepts Bitcoin payments, but I do not want to hold any private keys on the server. I am using the so-called "lazy API" method where I create private keys and addresses ahead of time off-line, and then get customers to send to them, and I want to be notified when the transaction happens, as fast as possible, with 0 confirmations.

I can't figure out how to do this programmatically, unless I add the private key to bitcoind's wallet, which I don't want to do for security reasons. I'd prefer to do it in PHP, but I'll settle for whatever.

Answer 1

You don't need to check your own bitcoin client for a transaction to a specific address. You can use https://blockchain.info/api.

Also, since version .10.0 the bitcoin client supports watch only addresses which allows you to add the public key without the private key and observe transactions this way.