It doesn't sound permanent
From the patent application:
"...can be applied to a region of the body via an adhesive"
This sounds similar to a temporary tattoo or could describe a sticker where the circuitry is either deposited directly on the skin or attached to a flexible substrate secured to the skin. It hardly sounds permanent.
What makes this useful? / Why would I want this?
Currently using voice controls requires pulling out your device and speaking your query aloud. This is bad because the query is audible to those around you (makes you look like a prat) and the source of the query is ambiguous (could really be anyone in the room/noise). A throat mic removes both of these problems, it can pickup a mumble (inaudible to others) and the device can be sure that you issued the command. For a device with similar capabilities as the moto x or nexus 5 with always on voice via "ok google" command, paired with a wireless headphone or bone conduction (bone conduction is best as it does not interfere with normal hearing) and the throat mic the benefits are obvious. Simply speak to yourself under your breath and the query is answered (reads google now cards with tts) without removing the device. It basically covers all the times you had to type in a query because speaking aloud wasn't appropriate/feasible or not worth the effort of pulling the device out. You could do the same with an off the shelf throat mic, but they are rather bulky, this device has the advantage of remaining relatively nondescript.