I'm currently using a dongle called the Automatic Pro which comes with an unlimited subscription for 5 years and has some other features too. The initial cost is more than any of the strictly GPS tracking dongles, but it works out to be a lot less without the monthly subscription fees. It has a really nicely designed mobile app too, and you can do some other stuff with it which I haven't really found useful. There's also a cheaper version but I think you have to be connected to it via Bluetooth, so there's no real-time tracking.