We've had these in the Roswell center since January. They are attached to front and back shelves. The technology was originally designed to have the labels with embedded tech to go off if the package enter the wrong vehicle. In true UPS style, they are half-assing it.
The current way they are used is each preloader has a set of cars, with a scanner attached to their belt. The preloader scans the barcode in your truck, assigning the scanner for that truck. If the scanner scans a package that doesn't belong to the truck, the scanner goes off. If the preloader enters a truck the scanner isn't assigned to, the scanner goes off.
The problem is now that preload is concerned with scans on packages and is judged as such. There's a report of the percentage of scans the preload does, and they chase those scans. So much so they have people that just go around, scan a pile of packages and walk away. The regular preloader then just loads as normal with a pile of packages or double scans them (doesn't hurt). This is of course the way to achieve a false positive, to keep the PPH up for the loaders. The system wasn't designed for that, but when you only care about numbers, that's what you get.
The Roswell preload since January has struggled with the demands of keeping up doing this scanning and maintaining YoY performance, unfortunately we have been floundering for the past 6 months with late leave building times due to preload not wrapping up. They are having preloader a doing another task while not increasing the workforce to accommodate the new task.
Used correctly I can see this tech being good, but it's not, and it isn't. Your preload and drivers will hate the day you go live with this.