[piceas]

Have a bunch of them that release at regular intervals and float up to the surface.

Where it is and what is wrong would be a good start.

[EA-3167]

Where it is sort of stops mattering when "what is wrong" is inevitably "It was either forced to surface" or "It's microscopic wreckage."

[HeyLaughingBoy]

What is your plan for retrieving the 99.999% of them that indicate nothing is wrong?