Is it possible to use a sat-nav as a presence sensor?
Not unless the satnav has a way of communicating with the internet too - even better if it can make web calls or has an IFTTT channel.
I’ve not personally seen anything like that before
BMW does it in the US through its IFTTT service.
As you mentioned, any SatNav Device that can send a text, email, or webhook (post) could use IFTTT to turn on a virtual presence sensor in SmartThings.
So just comes down to the details of what’s available with the set of devices.