electric imp code to read a digital signal and react when it changes.

electric imp - read button

// Register with the server
imp.configure("button example", [], []);

// readButton function called every 100ms
function changeState()
{
    local pinState = hardware.pin1.read();
    if (pinState)
        server.show("pressed");
    else
        server.show("not pressed");
}
 
// set pin1 as a digital input with a pullup resistor and call changeState when the stateChanges
hardware.pin1.configure(DIGITAL_IN_PULLUP, changeState);

changeState();