The only way to do this project is an electronic switching system, which is based on an arduino and rf module connected to the computer/tablet. Whenever the arduino is cut off from the rf network or from the computer/tablet, it will act like a homing beacon to notify the authorities that there's a problem, then you can take action on the theft case. Software solutions are not enough for this case as even modded bios files can be replaced with originals when it is flashed without booting the computer by using shortcut keys specific to the bios vendor like windows + b etc. or usually tablets can be flashed via bootloader with original firmwares just by generating a goldcard.
And by the way, if the computers/tablets are restricted to use in just a single room, there's another alternative for it, if you can give more details about the situation, we can sort it out together.
Hope to hear from you soon, thanks.