That path has been explored. A GPS needs several things. Power, an antenna to 'see' the GPS birds and another one to transmit an 'I'm being stolen' alert.
Now if you are a scrote stealing traps ...... 1 - you disconnect the battery and 2 - you smash/remove or disable any antennas you see on the trap! Even if you load a trap into a van the GPS signal is masked so is pretty unreliable. In the back of a van your scrote has all the time he wants to remove/destroy any cover screws and 'remove' any tracking device. Sadly GPS and SMS jammers are ten a penny these days ......... illegal they may be but so's thieving other peoples property.
Consequently your ground owner knows exactly where he left the trap before it was stolen which is a bit pointless because unless he was really forgetful he knows that already!
An internal battery you say ....... more expense and maintenance problems and it doesn't get round the smashed antenna challenge. Remember you cant 'hide' the antenna as it needs to see the sky and most of the 'secure' part of the trap is beneath the casting plate which acts as a lovely rf shield!
On top of this you need an SMS or LoRaWan capable device to communicate with some sort of monitoring facility or the mobile network. Cost price is around £40 so add £150 to the cost of a trap, plus the cost of a sim card and monitor service AND the hassle of maintaining all of it, Say a fiver a month ........... 20 traps on a ground that's £100 a month for a tiny ground for a system that probably doesn't offer as much as a padlock with a chain to the nearest tree.
We HAVE solved the problem by approaching the domain from a completely different angle ( but I can't tell you how
) and expect to be showing the solution to the market shortly ...... was going to be at IWA 2021 but that has now been cancelled and we are stuck behind this lockdown!