Yes, we have! The same kind of RF doesn't work in that form, since it is attenuated strongly over that big of a distance. But the other interesting alternative we tried it mmWave radar, RF at about 60 GHz, the same band as 5G. This is much more similar to conventional radar, in that it would bounce off the face rather than passing through it like our current system. We found a few problems with this: 1. It faced the same issue as cameras. mmWave radar has a very low penetration in tissue, so it basically just bounced off the mouth. This only let us see visemes, which aren't enough to get to a low error rate as complete phonetic decoding can. 2. While mmWave radar can detect skin movement as small as a few microns via Doppler shift (given it's small wavelength), its spatial resolution with most systems is quite low. For example, it can tell that something moved 2 microns but within a 5cm x 5cm block. This coarse information makes it very hard to decode

That's why we weren't able to make something that can mount to your laptop. We're trying to make a necklace form factor at some point in the future though, but can't give a date on this!

What about something like a baseball cap instead of glasses? Or some sort of head band?