Thanks for posting Nemo. They are all right for people that really like push buttons. In many ways they are just another way to customize your AR if that is what you like. I do have a problem with the "faster" part of the advertising. I have done actual comparisons with speed from low ready to first shot with one gun using the std safety and the other already on fire. Among 6 of us all were just as fast getting off shots while activating the safety as when the person we were shooting against was already on fire.
If push buttons make you feel more comfortable ten it may be a nice option but dont let the advertising skew your decision based off of increased performance. I have tried them on an AR and dont like them, particularly for more precise shooting grip that involves the thumb "unwrapped" from the grip. For this a traditional ambi safety works very well.
No it does not work for select fire trigger groups.
Chris