"The best cars have electronic locks. You're gonna have to learn a new trick." ― Vinny
The signal cloner is only used on two vehicles: The Vulcan Spectre and the Kubra GTS. It is a necessary purchase if the player is trying to complete the storyline or get all of the achievements in the game.
Hold the interaction button until a confirmation beep is heard--The cloner will then display a steady green light. Now the thief can approach the car, open the door, and start the engine without issue.
Bug: The lights on the cloner may not always show the correct state. The best way to tell if a signal has been cloned is to once again approach the tenant and try to recapture the signal.