Hi guys, I'm new to the forum. Been lurking for a few weeks but decided to join today. I'm after a bit of advice.
I would like to install a device that will turn on or off a washing machine remotely Via SMS or at least turn the water valve on or off. I own an appliance shop and rent out washers and I have a lot of people that don't pay after a few weeks. So would like to send a sms and disable the machine or at least the valve so it makes them call us to repair.
Thanks in advance for any advice 
What have you tried?
What's to stop the customer from over-riding your device?
...R
I presume you mean the water valve that is already in the machine.
SMS might be a little more expensive than you think for a lot of devices.
There are better options with just the ESP8266 relay boards but you would have to be within range of it.
Also don't forget the metal case will attenuate a lot of the signal regardless of method except maybe Lo-Ra.
You would also have to get a suitable power take off (maybe machines main board) to suit whatever device you want to use.
I believe the usual way is a deposit that makes it more expensive to not-pay than to pay.
ballscrewbob:
Also don't forget the metal case will attenuate a lot of the signal regardless of method except maybe Lo-Ra.
I have tested various LoRa devices located inside my freezer. You can pick up the transmissions outside, but they dont travel very far at all, 10s of metres maybe.
Any remotely controlled device of the type envisaged by the OP would need an external antenna.