Ancient personal shield emitter
Palm-sized unit of Ancient design which, when placed on the body of an individual with the Ancient gene, will generate a field that prevents the user from encountering harm. An advanced dampening field prevents penetration by objects such as bullets as well as allowing the user to perfectly withstand a fall of almost any altitude.
When the personal shield is on, excepting respiration, nothing can be permitted to pass into or out of the person's body, even if they so desire. Audio communication is possible, but food and drink (as well as personal relief) must be dealt with while the unit is off.
Even the user cannot reach the emitter to disconnect it. A mental command is responsible for deactivating the device.
Hide and Seek - McKay finds a device in one of Atlantis's many scientific labs and believes it to be a personal shield emitter. He tries the device on himself, but soon regrets doing so.
Irresponsible - Sheppard and the team come across Lucius Lavin manipulating a towns population with the aid of a personal shield.