There are at least two companies that make MOB
alarms - when a crew goes overboard and alarm is sounded - I think they can also be tied into the auto pilot - there is also a
Radio direction finder as part of the package - I have seen them at a couple of Fish Expos and Boat Shows
Note that a person in the water can only be seen about 100 yard away from a small boat (recreational type, sailboat etc) - when the Coast Guard does a grid search pattern using their small fast boats the grid is about 200 yards apart - if my memory is correct that gives about 97% chance of seeing a person in the water with small chop -