Triggering device

• Alarm trigger of a sort
• Hidden trigger
• Concealed trigger
• Trap trigger
• Security alarm trigger
• Trigger for booby trap
• Booby trap feature

Wiktionary Word definitions in Wiktionary
n. 1 A cord or wire arranged so that when snagged or pulled by an intruder, it will trigger a detector or trap or a device, such as a land mine. 2 Any means of detecting intruders.

Wikipedia Word definitions in Wikipedia
A tripwire is a passive triggering mechanism. Typically, a wire or cord is attached to some device for detecting or reacting to physical movement. A tripwire may be a wire attached to one or more mines — normally bounding mines and the fragmentation type ...