We’ve built something like this into our Indoor Location app a few years ago, it was pretty fun!
What we did is, the Indoor app uses our Indoor SDK as normal, receiving (x,y) updates our the user’s position. Simultaneously, we’re running a Nearable scanner, and if we hear a Nearable, we “snap it” to our (x,y) position, and remember it. So essentially, the person with the smartphone acts sort of as a “crawler” for Nearable positions (:
Since it seems you already integrated Indoor SDK, you’d just need to add the Nearable scanner:
… and then a little bit of “glue” code to merge the Nearables and (x,y) together.