Stealthy? Have you actually seen somebody wearing glass? It's the most noticeable thing about them. During IO there were a bunch of Glass wearers wandering around Moscone and people couldn't stop staring (myself included).
Sure, everyone can see they’re wearing glasses. However, outside of our little tech circle, most people don’t know that those glasses contain a camera, mic, and location tracker. And even if a Glass-wearer gets called out, they can deny that they were recording or taking pictures (unlike if you point a camera watch at someone).
You could do much better by getting rid of the HUD entirely and embedding just a camera lens/sensor, which can be really small, into some normal glasses ... for spy pictures you don't need perfect composition ... 😓
You'd be much better off with something like this: http://www.amazon.com/Waterproof-Camera-Watch-Video-Recorder....