Israel has or had a cute device, it looks like a digital kitchen timer and flashes the parking fare zone and current time, when you reach the maximum time or run out of credit it turns off. It can also enforce "no return" rules and you can end your stay by pressing a button when you return to the car.

It is just fiddly to input the fare zone on those cheap rubbery buttons and you do need to take it to a store occasionally to fill it up with credit. If you want to overstay you would need two of these devices, I don't know if they had any security to prevent that. I can't find any pictures so I guess smartphones and a central database have made them obsolete.