Multiple uart connections

This seems to work for me:

function scanFunc(dev) {
  if (!dev.name || dev.name.substr(0,4)!="Puck") return; 
 // you probably want to check ID, not name
  print(dev.manufacturerData[0]);
  // do something when this changes
}
NRF.setScan(scanFunc)

You could increase the advertising interval for setAdvertising which would help a lot:

NRF.setAdvertising({},{interval:50, ...
// you'd have to experiment with values. Due to the way BLE advertising works it'll probably only pick up every third advertisement

In terms of fast connection, try something like this:

var lightAddr = "98:7b:f3:61:1c:22";
var characteristic;

function setLight(isOn) {
  var gatt;
// if we have the characteristic, connect, write, disconnect
  if (characteristic) {
    return NRF.connect(lightAddr).then(function(g) {
      gatt = g;
      return characteristic.writeValue(isOn ? 1 : 0);
    }).then(function() {
      gatt.disconnect();
      console.log("Done!");
    });
  }
  // otherwise we have to search for it first
  NRF.connect(lightAddr).then(function(g) {
    gatt = g;
    return gatt.getPrimaryService("33160fb9-5b27-4e70-b0f8-ff411e3ae078");
  }).then(function(service) {
    return service.getCharacteristic("217887f8-0af2-4002-9c05-24c9ecf71600");
  }).then(function(c) {
    characteristic = c;
    return characteristic.writeValue(isOn ? 1 : 0);
  }).then(function() {
    gatt.disconnect();
    console.log("Done!");
  });
}