Connect OMG to bluetooth pulse oximeter

AFAIK this is also being done for the BM2 battery voltage?!? I suppose any temporary connection to receive at least one, or possibly two or three, notifications should be fine for most use cases, with anyone wanting to receive ongoing values just needing to send the request repeatedly with certain intervals.

This should allow integration into default OMG, while only the need for constant notification stream reception would require a separate build.

@puterboy

Just saw your ESPHome HA solution posted :wink: