From the Forums: Simple Web-Enabled On/Off Switch for #Arduino
Inspired by the Lockitron door lock, this web switch connected to some Arduino somewhere is as simple as it gets: it’s either on, or it’s off. (Funny too, someone else was playing with the switch while I was grabbing a screenshot!)
Basically this is a switch that uses AJAX to submit data to a PHP file every time that its clicked, and if someone else opens the button in their browser and clicks it, it will also move on your browser (open it on your phone and desktop at the same time to see it working).
I have an arduino turning an LED on and off in sync with this switch but for more important operations you might want to add a password