I have made this system for the lathes at work.
We needed some kind of system to send a message when they were running by them self after I was gone home, so they could alert me about something going wrong.
There are such modules made, but they are very expensive, so I thought I could make something on my own instead, and with the help from an Seeeduino Mega and a WiShield 2.0 I succeeded.
The system is still just on a breadboard, and is actually very simple.
To make it work, the light sensitive resistor is going to be mounted on the light on top of the machine. When something is going wrong in the machine, that light will turn on, and trigger the function in the arduino.
It could have been done a better and maybe more reliable way, but this isn't a critical system, and by doing it this way, it is leaving the lathe itself 100% untouched and totally insulated from the circuit I made.
When the machine turns the light on, the controller will check if it is on for more than 5 seconds, and then send a message, if it is on for less, it might just have been a flash from the sun from the window in a car passing by.
After the message is send, it will wait for reply from my web server and check if the message got send ok, if not, it will then light up the second led from the left, and wait 60 seconds before retrying, check again... and so on until the message is send successfully.
If the message is send successfully, the controller will wait 30 minutes (it only takes me 15 minutes to get there), then send a message again (in case I didn't notice it the first time), unless the light has been switched off.
After the light has been swicthed off, it will wait 5 minutes before starting to monitor the light again, so it won't spam me with messages while making the machine run again.
Sketch will be posted later, along with a sample sketch for my notice service for both iphone, android and email
The system I made is not using https, my system takes care of that instead, so the arduino can communicate directly with my system without needing any help from a computer to handle the https.