The "I'm a WP7!" app is mostly a fun tool to see other Windows Phone 7 users in your area, but it's also proven handy for spotting Windows Phone 7 prototypes in the wild. It discovered the HTC Ultimate, which turned out to be the HTC Titan in the US, and now it's found the Nokia Champagne, a previously unknown phone. WP Central notes that it was first seen on October 25th and appears to be running "Tango," a upcoming upgrade to WP7 Mango, which was released earlier this fall. Intriguing, sure, but there's no other information available on the device. It could be a US version of the Lumia 710 — or something else entirely — but it certainly heightens the anticipation for those who want  a Nokia Windows Phone 7 phone stateside.