Paul - I got a couple of these after reading about em on CF.
http://ultimatestreakfree.com/
No chemicals or anything needed - just a bit of water. And they do work. I haven't tried them on a bug encrusted windshield or anything like that - but on the "stay clean" windows of my Vette they work awesome. Also the best thing I have ever used on the interior windows of my DD's - use this cloth and follow behind with a dry microfiber and there are no streaks, and all the "chemical film" is gone. I love em...