If you just use wiring instead of bluetooth, you don't have a latency problem. The upcoming Pebble Core supports wired audio-out and microphone. Just strap that on your head, like I've been doing with the iPod nano, and you can talk to it (IF the Pebble Core has Android with speech recognition and text to speech).

I'm not comfortable with a 3G radio a centimeter form to my brain, perhaps 2G (Edge) is less problematic in that regard. Make it water-tight and I can use echo location underwater for navigation