I have something similar to this, that we used to use in S&R. It was the size of a regular chemlight, and worked off 3 button batteries. It puts out enough light to read by, but I wouldnt expect much more out of it than that. We used to tie them to the back of our packs, so the controllers could keep an eye on their teams. Worked well for that.
It would also work great to signal with at night. Tie a string to it & whirl it around. they need to invent one that has a whistling capability when twirling it, for signaling.