A microcontroller actively doing the current negotiation would be nice (for things like working at the maximum power of both android and apple chargers) but a m

A microcontroller actively doing the current negotiation would be nice (for things like working at the maximum power of both android and apple chargers) but a much simpler and dirt cheap solution would be to hook the data lines up so that they go through a simple filter that filters out everything other than the DC bias so power negotiation would work normally for chargers but no data could cross the cable.