Had some fun with my arduino decimilia, a Devantech cmp03 compass Module and google streetview.
I used the FirmataI2C library from funnel and wrote a simple as3 class to get my cmp03 working.
Then hooked it up to the google streetview api example via ExternalInterface, and had the compass heading set the yaw of the streetview.
Useful? not really
Fun? YEP!