Not sure how to really ask this but without adding any additional hardware what values/attributes can the Boron natively provide? Here is the list I have been able to compile thus far:
Power source
Cellular signal quality
Cellular signal strength
Other cellular values
Internal temp on the Nordic chip
List of bluetooth devices in proximity (haven't tried this yet, is this even possible? Does it need the antenna connected?)
That list seems right. You can BLE scan for nearby devices that are advertising.
On devices with the R410 or R510 cellular LTE Cat M1 cellular modem you can only get information about the cell you are connected to. Some 2G/3G devices can find information about neighboring cells.
The cellular network info includes the MCC and MNC, which identify the operator you connected to. That database is small enough for it on-device. You also have tower information, which sometimes can be used to identify your approximate coordinates, but that requires a cloud-based geolocation service.