About 10-15 years ago there was an Israeli firm showing a similar unit that never went into production but without the maps or GPS. It showed the boat, your buddy and any other divers within range wearing the unit. You could send a text from a list to your buddy or an SOS to all.
That unit would have been about $350 per unit and the boat unit came in two flavors, basic marking the boat for about $200 or a base unit that allowed you to send and receive text with the boat crew.