There are two ways to do this, and since I have a shared well that I share with other households, I use both ways. Contact a pump installer, and have a device installed that monitors pump cycles. If my pump runs constantly for a certain amount of time (open faucet causes longer run times), I have a red light that lights up. Also get a low water protection device. If someone leaves a faucet open, and the water level drops before you notice, this will shut down your pump to protect the pump and well. Other way of protecting the system, I have a shut off valve in the ground to each of the other houses. If someone is going away, I close the valve. When they are due back, I open the valve that morning. If they return sooner than expected, they have my phone #, and it takes less than 30 seconds to unscrew the cap above their valve, stick my long handle wrench in, and open the valve. By the way, in my area, we are allowed to have up to 5 total houses on a well for it to be a shared well. If there is more than 5, then it becomes a public water supply. I have water useage agreements in place only for the current users, so if any property changes hands, and I dont want to supply the new owner with water, then they have to obtain their own well.
Rob