@Ian Michael Gumby. I reckon half a mill is still outrageous.
I worked on a ship where we implimented a personell locator/lone worker system using the motorola UHFs and some badge responders. about 120 compartments wired up to a dedicated machine which displayed where everyone was, and linked into the Man Overboard and General alarms too - most devices had a panic button.
Whole package, hardware, transponders, cabling, and a terminal running some embedded software (OS9, I thihk) - around 20K UKP in the 1990s. We already had the UHFs with lone worker buttons, that was another 12K but was part of the comms package - I could make half-duplex phone calls home from mine.
1980s, I worked in a laboratory where we wore 'lone worker' pendants that called for help if we stopped moving or went horizontal, or pulled the lanyard off.. Around 1.5K total price, for 5 people in 6 spaces.