The QR code on the back of the Nexus One
If you visit that URL from any browser, you'll just be taken to the Android site. However, if you visit it from a Nexus One, you're taken to a themed memory game. (More on that here: phandroid.com/2009/12/15/nexus-one-holiday-memory-... ). That's it!
Oh, and by the way, the browser can tell if you’re using a Nexus One only based on the User Agent Profile which is easily spoofed. Long story short: some tweaking and you can play the holiday memory game yourself.
* Safari 4 – with developer tools enabled, go to Develop -> User Agent -> Other and type ‘Nexus One’ in the box.
* Firefox – type ‘about:config’ in the address bar and filtering on ‘useragent’ and setting it there. It’s apparently not quite as easy to do with the Chrome dev tools.
* Firefox method 2 (AG) – Use the User Agent Switcher extension
* Chrome – SOL
Seems like Google is looking to expand on Web Apps.