For me it's something that execute instructions and have their own instruction sets. It can be even built in a breadboard and you could eventually invent your own instruction set.
Even low powered microcontrollers have a CPU (microcontrollers are small, low powered computers), and microcontrollers can come in many sizes[1]
Your point could be that it's just a head mounted display on top of an ASIC, which I doubt it would be.
Right now I think Glass is just a display for smartphones and a way to use Google services, which I think is quite limited (you said it's useless without the net, I agree). Right now we don't even have the tech to run sophisticated speech recognition in a smartphone without a couple of servers crunching statistical formulas why would you think it would be different with a low powered device?
EDIT: Basically my last paragraph is saying that I agree with you but without being too harsh in the comments. This could be the beginning of the wearable computers revolution along with a iWatch.
[1]: http://www.wired.com/design/2013/02/freescales-tiny-arm-chip...