Another patent has "surfaced," adding more fuel to the firestorm of rumors that Microsoft has a Surface Phone in the works. The details of the patent are noted in a report by MSPU, and the patent technology appears similar to the touch-sensitive rear touchpad available on the PSVita.
Here is a picture and a description of Microsoft's patent application, named "Gesture Language for a Device with Multiple Touch Surfaces.”
"A gesture language for a device with multiple touch surfaces is described. Generally, a series of new touch input models is described that includes touch input interactions on two disjoint touch-sensitive surfaces. For example, a mobile device can include a primary display on a “front” side of the device, and a secondary display or touch-sensitive surface on the “back” side of the device, such as a surface that is opposite the primary display.
Accordingly, the gesture language can include a series of “back touch” interactions with the touch-sensitive surface on the backside of the device. Example interactions include direct and indirect touch input on the back side, as well as simultaneous touch input on both sides of the device."
Microsoft could be using this patent towards a completely different Surface device in their product lineup besides Project Andromeda. The full details of Microsoft's US patent application are available here.