I bought a Suunto heart rate monitor watch recently.  Many reviews said the watch crystal was too soft and scratched easily and they recommended this product. Sure enough the first time I wore it I scratched the face of the watch pretty good.  Not even sure how I did it but apparently it is really to scratch after all.

So I got some of this and I tried it.  It's a tiny tube but it doesn't take much to treat a watch crystal.  I followed the instructions and sure enough the scratches all but vanished.  You'll get several uses out of one tube before it runs out I think.

If you have a scratched watch glass give this stuff a try.  It might not fix really deep or wide scratches but then again it might.  I know the ones I had varied from light to medium and it took care of all of them.  Certainly cheaper than taking the watch in to a watch shop or replacing it.