I don't have anything as elaborate as the usual SMB-type rear bumper, just a single package-handler step. I installed a back up camera above my rear doors (raised roof/taller doors) and it works great for me---its the Ecco brand which tend to kinda spendy but great quality.
I myself would prefer visual monitoring over sounds or sensors. Here's a link to relatively affordable rear view cameras if that would interest you AnnieO: https://www.rearviewsafety.com/backu...a-systems.html
Once on that page you can see the entire site's product offerings. They seem to have a fairly liberal return policy which is a huge benefit.
These guys seem to sell pretty much the same stuff but at higher prices: https://www.tadibrothers.com/categor...camera-systems
My first and only interaction to date suggests they're a bit into the high pressure "buy it now...." approach--they'd rather you call instead of answering questions about their products.