A couple of years ago, I saw an English guy at SHOT Show with a device for shotgun training. It was a laser generator that went in the muzzle and had a wire that went to a ring that went around your trigger finger. When you touched the trigger, the lazer would come on and light up the spot you were "shooting."
It was a little unwieldy but a good concept. I've since recieved a training aid from Lazerlite that works on the click of the hammer but is designed for pistols only.
What was the name of that device, I think he may have had it at the Southern Side by Side, too.
Dick