Hi,
There was a bit of a laser-frenzy on local ranges over here, until everybody noticed that using the laser didn't actually improve their skills, but rather bluntly showed their lack of it
A device that I have used a number of times is a laser sighting tool. This device neatly pops in to the chamber (formed in 9mm para shape) and shows a nice laser dot when the toggle is closed. Of course, this thing is safe as it only helps as a measuring device, not as a sighting tool when shooting. (the Red-I laser).
It helps me to find any problems with sight adjustment and the lack of quality of my eye-sight.
I found my 1913 Dutch had a sight alignment problem towards the side and that my 1937 S/42 sight was pointing a bit lower than I expected.