We're currently looking at tracked lone worker systems, but I've not been briefed on those yet.
Ed, technically a single unit can be used by several employees. The alarm is received at the ARC and generates the start of your escalation process, whether that be to your nearest mobile, your own ops room, or the police.
This is where the self employed dog handlers have let themselves down and not pushed for this type of kit. How many handlers have tracked vehicles or lone worker alarms? How many have vehicles heat alarms for their dogs? I know it's a cut throat business, but by being the best, not the cheapest, you'll get the work!
Lots of people can walk around a site with a dog on the lead, but how many can stand up and honestly say they've covered every reasonable eventuality?