Custom bluetooth service on bangle.js

I've started building a web app that can connect to the bangle and send commands via bluetooth. All works well when using the built in service/characteristic:

const bluetoothServiceUUID: BluetoothServiceUUID = '6e400001-b5a3-f393-e0a9-e50e24dcca9e';
const bluetoothCharacteristicUUID: BluetoothCharacteristicUUID = '6e400002-b5a3-f393-e0a9-e50e24dcca9e';

however my aim is to stream accelerometer data from the watch, so I've been trying to write a watch app that exposes a custom service/characteristic to do this.

This is my first espruino device and my first use of web bluetooth - but as a start and following the code from this puck project: https://github.com/AkosLukacs/PuckStreaming/blob/master/src/PuckStreaming.js I've written a really simple watch app that I expected to expose a service that I can just read a value from -

function onInit() {
  NRF.setServices({
    '92c1b5b8-e824-4938-bbed-672529103e56': {
      '92c1b5b8-e825-4938-bbed-672529103e56': {
        notify: true,
        readable: true,
        broadcast: true,
        value: "Hello"
      }
    }
  });
  E.showMessage("Waiting..","Bluetooth Connection");
}

onInit();

Opening the app on the watch and then attempting to use this service and characteristic from the web app I get:

No Services matching UUID 92c1b5b8-e824-4938-bbed-672529103e56 found in Device.

Please can someone point me in the right direction as to why this isn't working?