There is a group doing them in Hartford, CT. Another article updated that.
The article quotes some damn law professor who is carping about the patrols and thinks that the residents should wait for Hartford to hire more cops. But the article also points out that the city is almost 100 cops below their authorized levels. And who is beating down the door to become a cop there? A cop there with some experience can take their POST certificate and go to a town with less crime and better schools for their kids.
So I guess, to the law professor, it'd be better to do nothing.