Matt & Michelle Day, SM#208 SV Talia
I am still building my marine experience, so you are far ahead of me. From a terra-firma perspective, motion sensors are used for their greater range verses IR sensors. IR sensors tend to get pretty expensive to pick-up a person/animal in a large back yard in the US.
I like your security idea, and by no means was intending to insinuate you eliminate that option. My thought process was that a 4-6 output IP68 digital switch (~$200) would give you many options to do both with flexibility and ease of install/maintenance.
For example, you could use the digital switch to:
1. Turn the light on manually with a simple wifi gateway and your cellphone (tender arrival) or some external device (i.e. FOB)
2. Turn the light on with a motion/IR sensor as a first alert sensor when on the boat (when you are on the boat)
3. Turn the light on when unwelcome guests board, but also send you a cellphone alert if the companionway hatch is opened (when you are away form the boat)
4. Send a cellphone alert if your bilge is running at a set 'excessive' rate
Maybe more than you want to take on, just what I have been noodling lately as an option for Talia.
SM#209 - Talia