US Patent No. 9,363,596 shows a diagram detailing a pair of wired earbuds with an internal accelerometer that can distinguish between a user's voice and ambient noise just by sensing vibrations in a user's bone structure.
The technology is in contrast to existing bone conduction headphones like the AfterShokz Bluez that transmit sound through your cheekbones so you "hear" the music rattling around inside your head. I've personally tried a few of these out myself and was underwhelmed by the audio quality, but it could be a different story when used in reverse.
Apple was also awarded another patent today in the form of No. 9,363,589, a "liquid resistant acoustic device" with a mesh umbrella that could potentially yield a waterproof speaker port for future devices. A similar component already exists in the Apple Watch.