Palm beacon

A palm beacon was a flashlight-like device held in the palm of the hand, often used by away teams in dark areas. 

Palm beacons were used when away teams beamed down to the dark and foggy planet Tarchannen III. Susanna Leijten later advised turning off the beacons as the light was frightening the Tarchannen III species. 

In 2368, Data modified a palm beacon to emit an optical burst pattern that would counteract the effects of the Ktarian game. 

In 2369, Neela and Miles O'Brien used a palm beacon while searching for tritanium traces in a deactivated power conduit. 

In 2370, Data and Captain Jean-Luc Picard used palm beacons after returning to an unmanned and non-functioning Enterprise after their three day search for a stray torpedo to discover that the Enterprise crew had de-evolved into various animistic creatures. 

Deep Space 9's corridors were equipped with storage lockers (similar to weapons lockers) that held three palm beacons and two tricorders.