VR controllers tracking uses IR photosensors and laser emitters to track the pulse. Based on the laser's flight time between the headset (or tracking station) to where the controller is, the positional information is calculated.
Referenced Sony
There are tracking station system and inside-out tracking system. The HTC VIVE uses a tracking station design, and the Oculus Quest uses the inside-out tracking system.
The inside out tracking system uses the camera on the VR headset to do all the tracking without tracking stations. The controller features infrared LEDs, and the headset camera continuously take images of them (constellation tracking system) to triangulate the position of the controller in space.
VR Gun Stock
VR gun stock is simply a lightweight boom that holds two handheld controllers for FPS gamers. The idea is to make the user easier to shoulder a virtual gun in the game to feel 3 points of contact.
Check out these VR gun stock to play your favorite FPS games.
VR Hand Tracking
Virtual reality hand tracking is the next level controller innovation to allow more natural hand gestures to interact with objects in the virtual space.
This allows finger tracking, gripping, squeezing, temperature sensor, touching and other haptic actions that a regular controller can't perform. This also means more natural and fluid hand motions for increased active presence immersion.
Currently, there are companies making haptic feedback gloves to mimic physical feedback to control the finger even if there isn't any physical object in the hand.
In fact, Valve has registered brain interface patent to create VR control system solely based on user's brain impulse to drive action. However, this technology will take years before it matures.
Meanwhile, Please check out VR hand tracking gloves here