It's not the first in-car head-up display we've seen. But it does make the most sense. Instead of packing in its own electronics and OS, the Hudway Glass Head-Up Car Display uses your smartphone as its brains. You simply launch a HUD app, set your phone down, display-up, and the aspheric plastic lens takes the image, flips it right-side up, and magnifies it up to 20% while letting you see everything that's going on behind it. It works with iPhone and Android, day or night, and is a smart alternative to standalone units.