Earlier this month the US Patent Office published a new Microsoft patent application covering an invention that relates to using wearables in a new way to control other devices. The wearable could be a ring or wristband, for example, and it would be able to control other smart devices around you such as a TV, a smartphone or HMD (think HoloLens). The wearable, being a small form factor, can't use a touch display for controls. So to use the wearable as a control device, it incorporates a microphone. The user could then, in one example, scratch the arm of their family room leather chair and that unique sound wave would be able to control changing channels or audio of a TV, or advance a tune on your stereo and so forth.
Back in 2010 Patently Apple reported on the use of sound waves from scratches that was illustrated in a video from Chris Harrison, a then third year Ph.D. student at Carnegie Mellon University. Harrison later went to Microsoft as a research intern as noted here.
Apple has two inventions covering the same idea. Patently Apple covered Apple's first patent application in 2011 and the second one last month. For more on Microsoft's patent filing, see our Patently Mobile report here.