I've tried my best at home with ghetto optics/techniques to get something near a collimated setup. Other than a trip to the optician with very specific values I don't see myself being able to collimate my cellphone's display. Without wanting to spend a couple of thousands AND needing to cut a hole in the dash panel of my car, I think the Glass is my cheapest (terms of money, time and effort) bet.
Why Google Glass will fail: When normal people who didn't sign agreements discover just how positively awful the "screen" is.