How can I use an iPhone as a controller for a flash game, as described here?
I don't think it's hard to do assuming your setup is something like this
phone --- remote server --- flash
The flash app and the app on the phone need to share a code to be bonded togheter. You can ask the user to insert a code manually or you can use a QR code.
The flash app use a socket to connect to the remote server, the phone app do the same. Both the apps send the shared code to the server and the server now knows that the input from the phone app need to be redirected to the flash app with the same code.