Here I am on a Wi-Fi equipped plane flying over the Pacific on a business trip to China and I'm able to check where my i8 is spending the night (on a ship moored in Southampton, England for the moment) since the ship it's on is tracked on a web site via GPS data.
Carac, since you indicated your ship is just about out of range for the Marine Traffic tracking, have you tried the Sailwx web site? This appears to cover the globe and uses weather reports that the ships provide, along with their GPS coordinates, to track their positions. I was able to locate my ship, Boheme, on both Sailwx as well as Marine Traffic.
Now if this was happening in early 2015 I'd probably be able to call the captain of the ship on my Apple watch to have him check on my car.