The Phone (2009)

Two mobile phones are placed in public locations. When these phones ring, random Australian citizens answer and are given an option: Press 1 for the chance to win a briefcase with $25,000 inside; or hang up. Those who choose play face a series of challenges outlined by the Clue Master. Failure to complete a challenge will result in money being removed from the briefcase. Once a contestant reaches the briefcase, they are given the option to keep all of the remaining money or to split it equally with the other contestant.