If I have a paid app on Android Market, will my merchant API callback URL get a hit when the customer goes to check out? I am wondering how merchants/vendors/developers secure their applications for android market.

I have used google checkout before to implement a custom integration, so I understand how that all works. What I do not see anywhere that I have looked is what, if any, integration does the merchant/developer have with the Android Market checkout process? I understand that the market uses google checkout, but in that case the market hosts the checkout process and not the merchant, so it's not clear whether they give your URL a call.

So where is the hook? Am I right in assuming it is the merchant API callback URL?