Thanks to my friend Jeff Q. for bringing this to my attention.  Gill Firearms has a forearm brace for Glock pistols.

The video shows some novice and beginner shooters and it appears to work. The shooters they used do not seem to know how to properly fire a handgun. You can see the majority of them using the teacup support grip. Where the left hand is under the magazine like the saucer of a teacup. This provides almost little to no support for recoil or muzzle climb. Now while I think an arm brace for a Glock is unnecessary when all you need is proper technique and practice, I do think that this arm brace has a use. Put it on full auto Glock 18 conversions. A lot of FFLs who have SOT have modified Glock 17s with a full auto sear. I have shot them and a real Glock 18C. The 18C was much more controllable due to the ported barrel and slide. I think this arm brace would make it much easier to shoot a non ported Glock 18 or converted Glock to shoot full auto.

Also, just like the SB Tactical pistol braces for ARs, this Glock brace could be beneficial for disabled people and help them shoot Glocks.

The Gill Arm Lock is $54.99 on Gillfirearms.com but they are currently sold out.