There are no APIs related to distance to the beacon in the Proximity SDKs.
This was a design decision by us—we consider building beacon-powered experiences based on the distance number alone to be somewhat of an anti-pattern, given how Bluetooth-based distance estimations fluctuate a lot, and are affected by the environment.
Instead, in the Proximity SDK, you define a Proximity Zone with your desired range, and we recommend building your experiences around this. (you’re either “inside” the zone, or “outside” the zone) There can also be more than one Proximity Zone, each with different range, per beacon, if you need to do something like “far” and “near” triggers.
If you share more about what app you’re building, and what beacon-based experiences you’re building into the app, we can help/advise further.