Well, friends, I have some bad news. It appears the Blockchain.info JSON-RPC API can not play nice with my payment module in its current incarnation. The payment module relies upon immediate acknowledgement of a transaction (0 confirmations) in order to function properly. There is a delay between sending payment to a Blockchain.info MyWallet address and Blockchain's acknowledgement of the transaction. It appears to wait until 1 confirmation. This means that it is impossible to do a slick immediate recognition of payment (as my payment module is programmed to do) with the Blockchain.info API at the present.
I could write an extension that would accept any order regardless of whether payment was ever sent, OR I could write an extension that would instruct the user to wait 10 or 15 minutes to see if their order went through. Both sound like a rather silly way of doing business, but unfortunately that's all that would be possible with the Blockchain.info JSON-RPC API (until they improve it).
This is a shame. Could you possibly make a version that shows a button "click here when you have sent payment", that will close the window and put the order through regardless of payment? I know this is not ideal but it would be no harder to check if the payment has been made than it would for say a bank transfer payment. Thanks for your time on this.