When carried in a holster that covers the trigger guard area, by a properly trained and practiced shooter, Glocks are no more likely to be involved with problems than any other weapon. They are unforgiving of errors, as are virtually all handguns, and the addition of "extra" devices to "improve" safety is usually an attempt to solve a software problem (you not being comfortable with the Glock) by adding extra hardware (things that make it harder to fire, both by mistake AND purposefully, when you need it).
Please consider the amount of manual dexterity it will take, in a somewhat unnatural direction (side-to-side), to eject that tiny trigger block before you can use the weapon to defend your life in a highly stressful situation. Also consider what will happen if any part of your support hand/fingers/thumb is in the way when you try to eject the device.
If you decide to "go" with this device for serious purposes, I recommend you ALWAYS use it, for every shot fired from a holster or low-ready position, EVERY time you hit the range. No exceptions. If you can't eject it 100% under calm range and/or competition conditions, then you should reconsider its use for serious purposes.
I tried it, helped others try it, and we ALL found problems with it in actual use. And I can assure you that the uncomfortable feeling about the Glock trigger action goes away once you are trained and practiced in its use.