I have a Dryfire Mag for my G19. I used it for a little while shortly after I got it but I stopped using it when I discovered the superior value of a laser cartridge for dryfire practice. The Dryfire Mag doesn't reset the pistol's fire control group, it only interfaces with the trigger, so it can't be used with a laser cartridge.
I eventually got a SIRT 115C laser pistol, which doesn't need to be cycled between shots.
However, I still use a laser cartridge and cycle the slide on my G19 for a lot of my dryfire practice. I had to train myself to maintain tactical discipline when cycling the slide during dryfire practice - I tap, roll & rack to cycle the slide, just like I do to clear stoppages. I also had to train myself to maintain safety discipline too, to make sure I took my finger off the trigger and out of the trigger guard when I rack the slide. It's easy to get sloppy and ingrain bad habits.