GATT service on RuuviTag

Well, I just tried your previous example here with 0x180D (and on-board temperature so it works on other devices) and it works fine:

NRF.setServices({
  0x180D: { // heart_rate
    0x2A6E: { // heart_rate_measurement
      notify: true,
      value : [Math.round(E.getTemperature())],
    }
  }
}, { advertise: [0x180D] });
setInterval(function () {
  NRF.updateServices({
    0x180D: {
      0x2A6E: {
        value : [Math.round(E.getTemperature())],
        notify: true
      }
    }
  });
}, 1000);

You can't 'read' the service because you didn't specify readable : true but you can get notified about changes. "NRF Connect" complains that the data isn't in the right format, but it does receive it.