Detroit, Michigan stars Eminem and Kid Rock have been challenged to a freestyle rap battle, which could pocket their chosen charities $1 million.

The offer comes from the producers of new movie Rap Therapy, which chronicles one Detroit social worker's efforts to use hip hop to help steer troubled teens away from gangbanging, drugs and violence.

The rap challenge will officially be launched in Detroit on Tuesday.

Blake LeVine, the subject of the film Rap Therapy, says, "It will be a televised rap battle and the winner will pick up $1 million for the charity of his choice."

The documentary features footage of 50 Cent, Diddy, Anne Hathaway, Fergie and Tom Cruise, talking about the benefits of hip-hop as a tool for kids involved in gang violence and abuse.