Great idea! Dry fire practice is a big part to mastering the use of any firearm. Given the price of rifle ammo and the time it takes to drive to the range, this device will make it possible for lots of folks to practice more often. That is a very good thing to do. Greatly improve your on target results. Sincerely. bruce.
This is also very compact (about 1.5 cubic inches) and can be used on any handgun or rifle that has a mounting point (or can be attached to a magazine base). It's useful during dry fire and live fire as well. Works equally well on iron sights, red dot equipped handguns and rifles and optics equipped firearms.
In related discussion... been thinking about ordering one of these mounts for use with a spotting scope. I've got a couple iPhone5 that aren't doing anything. Looks like it would be a lot more convenient than having to get exactly behind the eyepiece every time.