Meet VR Guardian: a virtual reality barrier system that keeps you safe as you play games and explore immersive virtual worlds. It comes with 4 Bluetooth sensors and 2 wristbands to alert you when you approach your defined boundaries.
VR Guardian lets you create your own safe play area. You get an alert on your wrist when you are too close to your defined boundary. The system works with the Oculus Rift and other VR headsets. More information is available here.