This is all you need to know.
Basically, a 'tracker' like in that scene.
It should be a one-handed piece of equipment of moderate mass (5kg lets say) so you cannot use it while you have a two-handed weapon out but not be completely helpless. (Pistols/Grenades + Tracker combo)
This tracker should not be available to begin with, maybe available by the early-to-mid game transition period where you need to have conducted an autopsy/interrogation before that "species" will appear on the tracker. (Eg: Researched Caesans, but did not research Sebillians - therefore tracker does not pick up Sebillian signatures)
Balancing measures that can be implemented include a limited range (~10 tiles around user) and it being some unreliable (10% chance to get accurate location of enemy otherwise it picks a random tile within 4 tiles of the enemy -- rerolls chance upon new turn) and also no indication of vertical direction.