Google.
More and more Google is beginning to remind me of the little drones from Portal.
[The turrets say this when you leave their field of vision]
"Hello"
"Searching"
"Canvassing"
"Sentry Mode Activated"
"Is anyone there?"
"Could you come over here?"
"Are you still there?"
"Target lost"
"Can I help you?"
"Searching"
Quite creepy mental image actually.