You need an interface that detects the door has opened, and instructs the mobile phone to send a text message. Mobile phones usually have an interface port on them that you can connect to, in order to make them do things like this. The interface needs a micro-controller that needs programming in order to do all the work, and supply the message to the phone.Your talking to an idiot Nigel pls explain how
This is not going to be inexpensive. I've seen cellular modules available at Sparkfun and they're ~$100 IIRC. That's not to mention the monthly cell service fee you'll have to buy from a cellular carrier.I am just looking for an inexpensive way to monitor my cabin in the mnts. It has no electric so I doubt a cell phone would last long.