Android publish app market automate post purchase tasks

If one publish's an app to the Android Market place and post-purchase/download tasks need to be carried out upon the purchase of the app by a customer through the marketplace, how can this be automated? For example, my Android app might require r开发者_C百科emote connectivity of some kind and so a username and password must be emailed out to them after they have downloaded my app + a record adding to my database..I know I must write a web service of somekind but cant think where to start :o does google checkout accommodate for such post-installation processes?

I am not sure if there is a post-installation callback that Android provides, but this sounds like something that can be done on first startup.

You could have a boolean in the application preferences that is used to determine if the your applications 'setup' has been completed. Any time the application is started, you check the boolean, and if they have already completed setup, you do a typical start, otherwise you prompt the user to go through the setup process.