The Particle has a BT radio, but I can’t find any reference online to talking to the Particle as a bluetooth device directly from another bluetooth device (like a mobile device). Is the only use of the BT radio allowed through the mesh functionality?
The Bluetooth API hasn’t been implemented and exposed us developers quite yet. That’s on the roadmap and one of the popular feature requests. At the moment, you have 2 options: you can use the BT functionality if you do a monolithic build (about which I know very little), or just wait until Particle bakes the BT functionality into the device OS (which could be a few months, or more, away.)