There seems to be a weird bug with the simulator. Notifications doesn't work inside it. (The permission doesn't show up either.) So to run this lesson you must deploy to the local machine...
That is sweet. I have previously been thinking about solving scenarios like this with NFC, but there's not really enough devices with NFC chips yet (and if Apple doesn't include it in their devices an NFC requirement will never fly with actual customers).
I'm assuming the QR serving bits are based in part on your "building your own STS" series? (I will be working through those posts.)
You also mention that the WP app is on codeplex - would you be able to share the link?