ESP32 as reader to Bangle.js

If you're thinking of multiple Bangle.js then make them advertise the data over BLE with NRF.setAdvertising.

You can then use ESP32 to read that data. If you're using Espruino on it you can do NRF.setScan(...).

To avoid having to parse un-needed advertising packets it'd better to use manufacturerData so you can filter out the devices.

So:

// Bangle
NRF.setAdvertising({},{
  showName:false,
  manufacturer:0x0590,
  manufacturerData:[1,2,3] // your data here as a series of Bytes
});

// Scanner
NRF.setScan(function(device) {
  // data is in  device.manufacturerData
}, {filters : [{ manufacturerData:{0x0590:{}} }] });