A handset identifying itself as "iPhone 3,1" was tracked by PinchMedia in its application iBART for San Francisco public transportation. According to MacRumors, iPhone 3,1 appeared in its usage logs during November.
The reference could signify a new iPhone model with major hardware changes, as Apple only changes the first number in a product's identifier string when it receives a significant upgrade. The current iPhone 3GS carries the identifier iPhone 2,1 while the original iPhone identifies itself as iPhone 1,1, and the iPhone 3G -- which featured minor architectural changes from its predecessor -- is iPhone 1,2.
Apple's use of 3,1 implies major and distinct changes, a practice that it also uses with its Mac lineup. References in software to an iPhone 3,1 have existed for some time, but the alleged use of the unreleased hardware would be a first.