here's what looks to be a good idea, Rainpal..............
http://www.rainpalevolution.com/
Those of you who can remember the 1960's will now doubt remember the rotating visor. It was a very simple idea where the visor was a circular dish - convex facing forward. On the edges were little moulded curved fins. The whole thing sat on a axle at the centre and the faster you went the faster it rotated. No chance of any rain staying on that of course.
I can imagine there were a few downsides. The vibration at speed would obviously melt you brain, and never scratch you nose or you would lose fingers and licking your lips could render you mute!
I used to have the Bob Heath "flick wipe". Basically a bit of wiper blade fixed to a tube of rubber that you wear over the index finger of your left glove so you can wipe the visor effectively with just a flick. Worked pretty well IIRC, even removing road salt and other crud. Happy days when the bike was the only transport through the winters of 81 and 82. ???
http://www.amazon.co.uk/Bob-Heath-Wipe-Medium-Black/dp/B006VC9DRM (http://www.amazon.co.uk/Bob-Heath-Wipe-Medium-Black/dp/B006VC9DRM)
They still do them!!!