Tried it out a little this afternoon and tonight, and discovered that
(a) cats pay even more attention to the bright green spot monster than they do to the red one - from 40+ feet, taking good care to avoid shining the light in her eyes.
(b) the spot is visible on a building about 200 yards away by day - by night I could clearly see it on a sign about half a mile away.
(c) the beam is faintly visible in cool slightly humid air at night.
What I would have really liked would have been for it to include a diffraction grating that let it project two perfect circles side by side, so that I could play Mysteron...
Really not sure what I'll be doing with this - it's illegal for educational use at school level, so I won't be using it for experiments at work. I do occasionally give talks, but I think it's probably overkill for any venue I'm likely to visit short of a Worldcon.
Never mind, it's a fun toy, and that's enough for now.