Full Conceal had a prototype of their concept back at SHOT Show 2017. Pete posted about it here. Their original concept was a cut down Glock frame and the remaining grip/magazine would lock onto the frame making the pistol a rectangular brick. You would have to remove the grip/magazine and insert it into the gun to make it into a complete pistol.
At Triggrcon 2017 they are showing off their latest prototype, the Full Conceal M3 folding pistol.
Their folding pistol is based off Magpul’s FMG9.
The Full Conceal M3 folding pistol will retail for $1199 however you can preorder it now for only $999. I hope they will sell just the frame so anyone can just add their Glock 19 slide if they wanted to rather than purchasing an entire gun.