Any recommendations on a car back-up system? Not the TV screen type

I have a backup screen in my car and don't need/want another one. But I'd love to have it "beep" as I get close to an object/thing/person as a secondary warning to my own vision and the TV screen.

I know they make ones that only perform that function--just beep if you get close to something. But I was wondering if any of you had any specific recommendations?

What I'm looking for is pretty simple.

a) Something that would perform that function not just immediately behind the car, but somewhat to the side of the rear bumper as well. I think there are some that have fewer sensors that just go on the license plate, but not sure that would give the type of coverage I'd like.

b) IDEALLY, something that would not require drilling in the bumper. Not necessarily a deal killer, but I'd like to avoid if possible.

I have a large backup screen, so I really, really, don't want/need the screen. If my stupid camera thing had the beeping thing I wouldn't even be asking, but I've never felt very comfortable backing up my SUV.