I started using Mothers CMX Ceramic coating on my vehicles. If you get any over spray on the glass, plastic headlight / taillight lenses, or flat black trim, it doesn't effect it, and wipes right off. Just for kicks I did the windshield on my Toyota with it, and found that dried, crusty, bug juice comes off MUCH easier. Same with the bumper and headlight lenses.
So I'm guessing they didn't have to change the product very much to make it a, "glass cleaner". That said, I applied it to an already spotless windshield. Today the new buzzword in the automotive world is, "Ceramic". Anything with that printed on the label will sell. Reminds me of the whole "Polyglycoat" craze in the late 70's and early 80's.