MinimOSD's TX is NOT connected if there is also a "wireless serial link" in parallel (E.g.: XBee) in order to use a Ground Control Station simultaneously.
To use a wireless serial link and MinimOSD at same time, you need to make an "Y" cable or prepare your APM IMU board to have a parallel "mirror" connection.

Bellow is a picture of a nice solution using a bent 20mm long male pin-headers.

• Upper mirror pins: "TX" from MinimOSD is NOT connected on the APM's telemetry port input.
  
• Lower mirror pins: all the four wires are connected to the wireless serial link.