I say I haven’t gone too far enough.

Last year I bought a Particle Electron which is a little module that runs Arduino-like code, but has a cellular modem attached to it as well.  I mated it to a temperature sensor and GPS, put it in a weather tight box and I keep it in the cargo area of my car connected to a switched 12V power point back there–it also has a lithium-ion battery which can keep it running (with judicious standby times) for a couple of weeks between running the car.

The sketch that I have running on it reports the position of my car every ~30s while the vehicle is running (12V is present) and every 1-5 hours when it’s not running (no 12V), there’s also other data reported like speed, course, temperature, cellular signal statistics, etc.  The reporting is through a PHP script that writes it to a database.

This what you’d normally see, a traffic-overlay map with a Subaru icon representing the car’s location.  The InfoWindow opens when the car hasn’t reported a position in more than 15 minutes, “Last Report” is the last report from the car and “Last Check” is the last time this browser pulled data from the server.  Temp is the cargo area temperature in the car and battery percentage is for the lithium ion back up.  The InfoWindow closes itself when the car is moving and the direction of the Subie icon matches the last reported course of the car:

I recently drove all over the place and I decided to see how the cellular signal was along the way so I put together a heatmap where the weights are based on the RSSI of the cellular signal.  I was pretty impressed with how good the signal is, but also the fact that the service works in other countries (like Canada too).

I assume the roaming from USA to Canada was seamless, but I do have a watchdog that may have restarted the device when no cellular was detected for more than 10 minutes.  That might explain the short blips around the border.