The DualShock 4's light bar was developed for Project Morpheus

The DualShock 4's light bar caused quite a fuss when the system launched because it was so darn bright and obtrusive. But you know why it was there? According to SCEE senior designer Jed Ashforth, "it was for tracking for VR."http://images.eurogamer.net/2013/art.../70/format/jpg
Ashforth spilled the beans on Sony's once secret plans for VR in an interview withTechradar. "The tracking light... it was our department that said we need that on," Ashforth explained."When all these things were coming out six months ago and everyone was going 'it's reflecting in my TV,' we were going 'oh no' because we couldn't tell anyone what it was for."On the plus side, a recent system update allows players to dim the light bar, while other games like The Playroom use its glowing feature in conjunction with the PlayStation Eye camera to track the position of your hands. The colour-coded controllers also work as a nifty Move substitute for Johann Sebastian Joust, so it's not all bad. It was just confusing as its true purpose had yet to be revealed.

http://www.eurogamer.net/articles/20...oject-morpheus