For directional indication, the $3K base needs three antennae, up high
for best results, on deck for best accuracy.

MOB with dismasting is a possibility.

User battery life? Change every month? Waterproof battery door, or
inductive recharger rack at companionway? Night light function?
Includes a whistle?

I have been a MOB and I lost an expensive floating hat in daytime
whitecaps, once. It's easy. If far at sea, I would even like an
aluminised retro reflective hologram hydrogen balloon on a string with
a fishing kit, water still and umberella. Any proper 'brolly for a
sailor includes a lifejacket with integral harness, anyway. Any of the
soon to be mandatory sailing helmets should include a schnorkel and
breath still, if nothing more. Some kind of grease to minimise skin
osmosis and chase sharks might also help.

Might not this neck lanyard float away from a snoozing popeye? Maybe
the sailing helmet would be large enough (with chinstrap snug) to
prevent it's loss. How about a sonic alarm to remind user to do up his
chinstraps?

Cost benefit? How better to spend the money?

How to get the crew believing that a battery toy is better than a
lifejacket, lanyard and survival kit including a whistle and an
umberella. What kind of discipline is that, Darwinistic?

No wonder the ecology is getting screwed.

Terry K