I didn’t think a coach was allowed to use a radio on the bench. If you look at the espn video of the US-Costa Rica match at the 70:30 point, you will see the coach of the Costa Rice team speaking into a microphone on the collar of his coat.
USSF answer (November 2, 2009):
We supplied this answer to another questioner back in June. We believe it will apply to your question as well.
Under FIFA rules of competition, suspended coaches are neither forbidden nor allowed to communicate with their teams via mobile phones during FIFA matches. FIFA will not take any action. Nor is there anything in the Laws of the Game or Q&A to cover this. Accordingly, subject only to the requirement that the team official behaves in a responsible manner, mobile phones, headsets, walkie-talkies, and other similar communication devices may be used in the technical area.
To ensure better compliance from its teams, perhaps the league should provide more complete rules and guidance to the teams as to what constitutes “suspension” and what a coach or other team official who is under suspension may and may not do. It is not up to referees to police disciplinary rules of a competition.
To this we can add only this further clarification: The coach may not communicate with his players via a telephone of any sort.