Simple Beacon for Android SmartLock workaround.

Thanks for posting it up - it looks good!

The only thing I'd say it generally using Strings as arguments to setInterval/setTimeout is considered bad form in JS (and usually you'd just use functions like setTimeout(function() { ... }, 1000)), but honestly there's no good reason why it's bad on Espruino (Strings are actually faster) other than that you don't get the command syntax-highlighted/linted in the IDE.

What's a better set of arguments for the watch to detect, say, a press of between 50ms-100ms?

Ahh - yes, there's a trick to it :) If you detect the falling edge instead of the rising edge, then you're called when the button is released and you can compare how long it was held down for:

setWatch(function(e) {
  var d = e.time - e.lastTime;
  if (d>0.5/*seconds*/) console.log("Long press");
  else console.log("Short press");
}, BTN, {repeat:true, edge:"falling", debounce:20});