Pheromonic sensor
The pheromonic sensor was a type of sensor commonly used on explosive devices. They were triggered when a particular individual or species came within range. 

Ferengi locator bombs use pheromonic sensors to lock onto their target, and Flaxian assassins were known to favor pheromonic sensors. ()

In 2371, Elim Garak used a pheromonic sensor to trigger a bomb in his shop, thus implicating the Flaxian assassin Retaya on the station and instigating an investigation. ()

See also
Pheromone
Sensor technology