Using an LED Pulse Counter

I just gave this a go on Puck.js with an LDR between D1 and D2: http://www.espruino.com/LDR

var counter = 0;

function update() {
  var a = new Uint32Array([counter]);
  NRF.setAdvertising({},{
    name: "ELEC",
    connectable : false,
    scannable : false,
    manufacturer:0x0590,
    manufacturerData:a.buffer,
    interval: 600 // default is 375 - save a bit of power
  });
}

D1.reset();
pinMode(D2,"input_pullup");
setWatch(function(e) {
  counter++;
  update();
  digitalPulse(LED1,1,10); // show activity
}, D2, { repeat:true, edge:"falling" });

update();

It works amazingly well - I'll try and stick a video/tutorial up soon.