I've had one for more years than I remember. It's only a couple of inches long:

Small glowstick by Civilized Explorer, on Flickr

It's small, thus handy to carry around. I have very bad eyesight, but I can easily see the glow in the dark and find whatever it's clipped to. I clip it to a flashlight and whistle when I'm in a hotel to I can easily grab the stuff if I have to evacuate in the dark. When I'm camping, I clip it to whatever I'll need in the dark if I have to leave the tent. I haven't needed my survival knife at night, yet. :-> Just the toilet paper.