I think the way to do it would be that you have GPS run a update script to sync the devices. Surely the boat has a GPS, right? Or there's a GPS somewhere in the system.

So to refine the gp's question: surely there's a way to push an update or sync with a script that can do this based on GPS coordinates, right?

I would think a syncing mechanism would be a big help anyways since regardless of the reliability of the GPS script you're still going to be doing this, right?