Time-of-flight is like knowing (dt_[1, 1] = 0,) dt_[1, 2], dt_[1, 3,], .. dt_[2, 3], .. dt_[n, n] for all inter-beacon times, and I'm assuming bluetooth signal travels through air in essentially constant time (doing any muxing of bluetooth "channels", if such a thing need exist, to prevent "overlap" of bandwidth?).

So do you have some kind of convex hull program that finds a shape of (dx = v * dt), where any predicted dx_[1,3] >> dx_[2,3] + dx_[1,2] implies some line-of-sight obstruction between beacon 1 and beacon 3? Especially when combined with dB of signal strength versus mere "dx" quantity alone?

I guess I'm wondering what the typical resolution is of a floor plan, how many beacons are necessary, and what kind of algorithm can crunch all those numbers into a neat path-planning-type solution.

edit: I'm quite the fool this morning, having not read the post before commenting! Nicely done. Looks like a sweet product. Hope you're able to grow the company!