Mimic brain interlink device
From The Stargate Omnipedia
An odd-shaped device which interfaces directly with the forehead of human forms, allowing a mimetic alien with a mimic memory device a direct interface to the subject's memories. This can be extremely useful in posing as that individual and remaining under cover.
If the device is removed, alarms sound and the corresponding alien is immediately alerted.
KEY EPISODE
Foothold - The Fraiser duplicate alien realizes a data transfer has been interrupted, and goes to see what has become of the actual Dr. Fraiser's interlink device.