Cuts the vehicle off? Can't see this as a device a vehicle manufacturer would fit given its impact upon powered steering, assisted braking, hydraulic sytems etc. There are vehicles with manufacturer installed sensors that apply low speed braking or provide proximity warning to a driver but none that I am aware of that would stop the engine. Retrofitting none OEM devices leads to some pretty murky waters regarding employers duties in relation to work equipment

Emergency braking systems IMO are only effective in straight-line vehicle traffic situations and are reliant on Doppler and camera image recognition and computation. I very much doubt they'd work in the situation you describe. As others say, retrofit would be fraught. Any banksman or reversing assistant who places himself in the situation you describe should be disciplined!

OAre you after something like Myzone ( others available ), doesn't break the vehicle just sends an audible warning to the person in the plants immediate area. Gap in the technology seems to be that the driver doesn't get a warning to my knowledge.

All these gadget for people who do not pay attention on dangerous sites, Personally i feel they are a waste of money and people would be far better off with the correct training. Lorries should never reverse into a site unless there is a banksman. Like wise its his responsibility to ensure that there is no other workers in the area, and that everyone is paying attention. Gadgets like this is just a poor excuse for little or no training, and would offer very little help in a well organised site. From the various adverts its appears that worker will walk aimlessly into dangers path, with eyes and ears closed, or decide to set up a workstation in the path of a reserving lorry. There can be no replacement for competence, I would be very surprised if they had this on a site, instead of adequate training