Was thinking of doing one on Prescription windscreens for cars / trucks.....you know the sort of thing.... vari-focal, photochromatic windscreens with an option to upgrade to polarising. With the vari-focal, the bottom quarter of the windscreen is set to close up so you dont bump into the vehicle infront and the top three quarters is set to distance for normal driving.
For those who cant get on with vari-focal then there wqould be an option to get bi-focal with a clearer boundary between near and distance.