In theory if you could place a second bank of receivers behind your head and had an accurate distance between the two you could simply the problem to just requi

In theory if you could place a second bank of receivers behind your head and had an accurate distance between the two you could simply the problem to just requiring line of sight. It also sounds like they have a multiple device fix available, the only question being can they devise a way to synchronize two of the devices without requiring the user to do any measurements.