The landscape for car HUDs has changed dramatically over the last year, so here is a short overview for what’s possible.
Microvision supplies a Pico projector which uses laser projection to project onto a car. It works during daytime and doesn’t need a film to be added to the glass.
AAXA also delivers a pico projector, which it claims is the worlds’ brightest.
Superimaging has a windscreen soluiton, using an emissive projection display. It doesn’t use pixels, which gives an interesting look to it, no idea how the image is generated though. Some more information here.
Wikipedia also has an interesting article on HUD’s including the different generations.
Virtual Cable is an interesting system that puts loads of information on the windscreen, but nothing on how the hardware works. They overlay the route as a cable op the windsreen, and overlay other information on the windscreen too.
Smart HUD uses Android and the Microvision pico projector to turn your smartphone into a HUD solution. A tracker device is added to the steering wheel, allowing you to safely operate the device.
By far the best software is Atoll Ordenadores ASmartHud series of apps, which are unfortunately iphone only 🙁