This kind of technology is years away, but when it gets here, it changes everything. The primary limiting factor of smartphones today is display size and input efficiency. With speech recognition providing better input on the go, contact lens (or glasses) based displays which overlay a giant virtual screen over reality solves display size and makes a smartphone a much more powerful device.
Google is going to be first to market with viable augmented display glasses (Project Glass, starting this year) but making them disappear (i.e. contact lenses) is the next logical step. Really, though, it will take years to perfect this technology. I don’t expect it to be mainstream until near the end of the decade.
The obvious scenarios like turn-by-turn navigation and facial recognition with contact info (never forget someone’s name again!) are great, but in much the same way the ability to create apps that took advantage of new sensors in phones (GPS, accelerometers, touch, etc.) lead to apps that nobody could have foreseen, this technology will be fertile ground for new ideas. Exciting stuff… I can’t wait.