Earpiece

The earpiece appears in Infiltrating the Airship as one of the tools the Government provides Henry Stickmin with to enter the The Toppat Airship. The earpiece is one of four options that can be chosen in the first choice menu of the game. Choosing it starts the path that can lead to the "Government Supported Private Investigator" ending of the game.

When chosen, Charles drops Henry off on the roof of the Airship and uses the earpiece to stay in touch with him through radio. From here, Charles proceeds to guide Henry on his quest to find incriminating evidence against the Toppats. He also provides him with more tools and assistance along the way, like hacking into the Airship's power grid.

In Completing the Mission, Henry (and Ellie) are seen using it throughout three branches in which they communicate with Charles, including Valiant Hero (only seen in the Air Cannon fail), Triple Threat, and Special BROvert Ops.

The earpiece design itself originates in Stealing the Diamond, with Jack Sheen in Intruder on a Scooter using a earpiece. In the legacy version, it was more inline with the design that would be used in Infiltrating the Airship and Completing the Mission. However, in the remaster, due in part to his overhaul with his new helmet, the earpiece was redesigned to be slimmer.

Trivia

 * The earpiece can also transform into a Force Gun, as seen in the last option of the "Government Supported Private Investigator" ending.