I came across the Rufus Cuff “Wrist Communicator” which is somewhat interesting. It reminds me of “that thing that is on my wrist” worn by Leena in Futurama. It was also referred to as “Lojackimator” in one of the Futurama episodes.
One thing for sure, the “Wrist communicator” is not for everyone. It is a big enough to make it a little too geeky for most people. Despite its ability to run full Android apps, it does not replace your cell phone. It has to be tethered to your cell phone to be able to send SMS messages or answer the phone. It is unlike the Neptune Pine, which is a full fledge phone on a wrist. It does not support a color display, so it is limited in what it can do.
In any event, I question the viability of a full fledge wearable cell phone. The bulkiness and awkwardness is unlikely to appear to most people. How does one type on the phone when you are wearing it? Take it off? If so, that is exactly what the regular cell phone does. How about battery life of a device that sport a 3″ display?