When you strap on an Oculus Rift virtual-reality headset, you're free to look up, down and around. But as soon as you try to explore the virtual world further, you're stuck. You can't interact with your surroundings or walk across the room.New controllers and sensors hitting the market are built to solve this problem, whether by tracking the precise location of your fingers so you can grab that virtual gun or giving you a simple joystick so you can "walk" from place to place.