[curryst]

Some cars already have those. I've got a car from 2017 that has some kind of sensors wrapping all the way around the bumper. When I'm parked between two cars, it can detect a car roughly 15-20 feet away as soon as I get an inch or two of my bumper clear of the other cars.

It does lack any spatial indicators to the driver, though. It just plays a beep, but it doesn't seem to play the beep from the side of the car the danger is in, nor does it beep louder when they're closer. Still, it works remarkably well. Reliably detects pedestrians and vehicles (even while I'm moving, which is impressive, because it doesn't go off for parked cars when I start moving).

I think it's the Dodge ParkSense, but I bought the car used so there's a possibility it's something aftermarket.

It's saved my ass a number of times. I'm in jacked-up pickup truck country, so it is often impossible for me to see pedestrians about to walk behind me because of the lifted truck, and likewise the pedestrians can't see me until they're behind me.