Where do you get the idea that it's always on and streaming to google? Glass is aggressive about power savings.
I had a chance to try Glass last week in Chicago and I believe that the owner stated around 3ish hours of battery life for non-stop video recording. You COULD attach a USB cable while wearing them and keep a battery in your pocket.
Look at it this way: If Google had developed a new battery technology that fit in the current Glass profile AND was 'always on, always front recording' then Google would have much bigger news than just Glass itself.