I did try out a laser-based unit in August 1998. No CO2, just a re-setting trigger. The product literature made mention of a dry fire "module", which I presume to be a replacement of perhaps the trigger assembly in the frame, perhaps even to include the trigger bar.
It was expensive. I don't want the whole laser system--just a way to dry-fire.
Maybe I just shouldn't buy that Glock...stick to revolvers and get a 7- or 8-shot unit...