According an Ars Technica article, Google had built a prototype wearable that would activate Google’s voice search with a tap (think Ok Google prompt in a button form). It wasn’t a stand-alone device as it needed to be paired with a smartphone, and its capabilities were limited to whatever Google voice search was limited to (you can send messages, have it list your appointments, and start calls on a typical Android phone). Eventually, the project was mothballed, and nothing became of it. Instead, Google is working on different wearables right now, including a Google Glass successor that has no display. Motorola, which once belonged to Google, has also dabbled in wearables tech with an earbud called Hint.
I’ve said many times that our phones would eventually evolve into comm badges à la Star Trek as cloud computing becomes more common place, and the actuality of that vision was closer than I thought.