Interdimensional visibility device
From The Stargate Omnipedia
Cylindrical device believed to be of Ancient origin, discovered by SG-1 on P9X-391. Though the complete purpose of the device is still unknown, it has the ability to allow humans (and possibly other sentient species) to perceive alien creatures that exist within a parallel realm. The crystals that power the mechanism can be reordered in position to generate various outcomes, including turning this perception on and off.
Anyone who touches the device receives this extra-sensory perception, which is spread to others via physical contact.
KEY EPISODE
Sight Unseen - SG-1 returns with an alien artifact from P9X-391 and discovers it has the ability to allow people to perceive extra-dimensional beings.