Looks interesting, I'm not a fan of bump fire because it is hard control safely, generally wastes ammo (but it's your money), and my biggest concern is that I have a suspicion that it makes you more prone to having an Out of Battery Detonation causing an ensuing KaBOOM. But Slide Fire Solutions has finally came out with their SSAK-47 stock and Military Arms Channel has a review here:
Overall I think it is interesting and has some merit, more than I initially though it would due to my person dislikes of bump fire. I like how the knob can be turned for both semi and bump fire. It definitely makes bump firing safer, my concerns are still feeding it (I'm poor these days LOL), if you can use the semi function with the other hand because I do a lot of ambidextrous firing drills, and I still am afraid that it can increase the chance of an OOB. It will be going for around $290 so it isn't the cheapest toy for the AK either.