I have seen people market a lot of stupid junk for SCUBA, but I think this is pretty clever and has some overall redeeming value.
It will quite obviously soon be bought-up by a major mask/SCUBA manufacturer and will be available as part of a built-in mask device.
Downside? You only have a choice of "two different signals", but hey- that's more expressive than just banging on your tank. And it does give you some sort of "distance" indicator that works up to maybe 100'. See
http://www.affinitydevices.com/B-Link_User_Manual_Rev_9b_18May09_a.pdf
I do agree with RJP though. Most of my dive buddies, all I do is use a flashlight and tik-tik-tik against my faceplate, or with any Diveguide DM, I just snap my carabiner link.
This gadget would work well with signaling my wife, as taking hand grenades diving has become problematic since TSA.
If it appeared at DEMA, no one noticed it, at least not in the realm of Certified Internet Divers.
I like where this device is headed.
Buddy-Link: Connecting Divers... In the Blink Of An Eye