In-frame devide would be perfect, as it takes some time for thief to take the bike into parts.
Then something which would constalntly supply the batteries (of GPS) with power, let's say, never drop below 50% of the battery capacity. Like, batteries of light would be connected by inframe cable to the batteries of the GPS
All rechargable. (and that light batteries would charge those inside the frame
)
Or maybe those small GPS devices aren't eating much power, then just some megabattery would be fine, and once a year to change it, wouldn't be a problem.
Problem would be if the device fails to send any signal
like, when they would hide the bike in some deep nuclear bunker.
Edit:
Btw I also saw a locker which contains some chemicals (colors) which will paint the thief, but he eventually can still steal the bike.
But maybe it can be changed to put some H2SO4 to the locker ?
Or some high voltage shocker.
Or some device which will buzz me on the phone (or watch) when the locker is being opened (sort of silent alarm)
Or maybe, never leave the bike alone