it's a fake arm. There is actually several H6flex drivers, a multi-cell high capacity LiPo pack, and a little hamster running in a wheel inside RHD's "arm"
Sadly, it doesn't seem to peak over 1.2W anymore (that was the highest I could get it to off video - but it drops quickly after a bit of usage). It used to hit 1.5W. It may just have low batteries, given that I haven't used or charged it in 2 years. It's been in a drawer since my initial post (for obvious reasons I never actually wear it). The watch mechanism's cell is completely dead and needs replacement.
Still an absolutely amazing build :beer: The covert nature of it along with the micro electronics and power source are brilliant. Thanks for the update.