Variable Window tint: Would you use in 911?
 

This would seem to make more sense to use in hot climates but others prefer the privacy as well. Are there applications for racing?

It looks to be a film that is laminated into glass. Perhaps in Lexan as well. Looks like an opportunity for a company to make retrofit windows.

http://www.refr-spd.com/index.html

IMO, if this could be produced in external film form and applied as the current stuff you'd have a huge seller.