The most promising tech for real-time location sensing right now us Ultra-Wide-Band based tech. You need sensing times in the picoseconds, but apparently that's

The most promising tech for real-time location sensing right now us Ultra-Wide-Band based tech. You need sensing times in the picoseconds, but apparently that's actually doable. This guy managed to get one of these systems working, and when last heard from was preparing for a Kickstarter: http://www.mtbs3d.com/phpBB/viewtopic.php?f=138&t=15623 http://www.mtbs3d.com/phpBB/viewtopic.php?f=138&t=15623 And XSens have a fully-working system, but it's Not Cheap.