Just be careful if you do buy glass, that you don't buy a terribly "cheap" one.
I made that mistake - in addition to at least one other mistake
Here's what I picked up: http://www.amazon.com/gp/product/B005EVPZJQ/ref=oh_details_o00_s00_i00?ie=UTF8&psc=1
After installing my glass screen protector on a 5D Mark II, I managed to crack it and cut my thumb at the same time just a couple weeks later!
I was simply pushing the body into a neoprene case, and that pressure was enough to crack the inexpensive glass.
Of course, the glass was not tempered, and cracked into what seemed like a hundred small pieces – all of which were stuck to the camera!
Fortunately, the camera was not damaged – but obviously a frustrating experience.
I'll go film protectors from here on out.
Ps. I was traveling when the protector broke. I ended up buying a film protector for a smart phone and cutting it to size. That was months ago and it's still holding up great!