Have any of you tried one on your camera or lens ?

http://www.camerarmor.com/index.html

Interesting idea - I've seen it advertised but not one in person. I'd be a little worried that it might hold moisture if you're shooting in a damp or wet environment, so I probably wouldn't leave it on the camera all the time (especially during storage).

I did just purchase an Invisible Shield (http://www.shieldzone.com/) for my Olympus 720SW which tends to get banged around a lot. I have seen these installed and it's hard to tell that anything is on the display. Check out the video with the covered ipod that they toss around in a box with a bunch of screws... Water won't get behind this shield so it's not a concern - it only covers the LCD display, at least in the case of a camera.