That's the AN/TPQ-36 and -37 *firefinder* counterbattery radars. They work.
They can pick up fired mortar rounds in flight, send out targeting data to a field artillery Fire Direction Control center, and have rounds fired and on the way before the mortar shells land.
The original versions with which I worked were based in 2½-ton trucks; the current systems can be moved by a standard HUMVEE. They're getting there. The Marines had one atop the barracks in Lebanon that was destroyed by the truck bomb, I believe, set up to coordinate naval gunfire in response to mortar or recon attacks against the Marine barracks...and so instead, the terrorists resorted to a truck bomb for their attack. *Firefinder*.
I'm sure their locations are kept low-key, but if it can effectively return fire to a sniper's position, it too can be hit.
I also saw the shot-finder on the Discovery Channel program discussed above. It worked totally on acoustics. Deploying them in big city hoods is surely underway.