Sure, right now those microphones are tuned to pick up a certain frequency range to "hear" gunfire, but just how long do you think that it will be before they can be used to zoom in and hear normal conversations while a subject is walking down the street under camera surveillance? Think it can't/won't happen? I have a bridge for sale...
And the courts will be happy to tell you that you have no expectation of privacy on a public street so whatever they do record becomes theirs to use against you...