Here is a location tracker with a solar-powered battery that lets you keep an eye on your vehicle and other assets. The Linxup LAADS1 can report location every 3 hours when stationary and every 10 minutes when in motion. It comes with a weather-proof case, so you can use it in marine environments.
The device has a 10600 mAh battery and should last up to 10 years. You can use it to track trailers, cargo units, and non-powered equipment.