homing device
From Longman Dictionary of Contemporary EnglishRelated topics: Weaponshoming deviceˈhoming deˌvice noun [countable usually singular] PMWa special part of a weapon that helps it to find its targetExamples from the Corpushoming device• He walked around the corner to his frontdoor, key pointed like a homing device.• In there they all carried a small radio homing device, to find each other blindly if necessary.