Real cops with real guns probably won't respond any quicker to 911 calls, but you will be able to buy a copy of the video of you snapping off that double tap into the guy who trys to rob you.
Out of curiosity, is open or concealed carry legal in the cities where these types of surveilance devices are being installed? Most of the places I've noticed these things going on seem to be really anti self defence, especially with guns.
More likely that double tap photo will be given to you free at your trials, one in the criminal trial and one in the civil suit by your attacker or his survivors.