There is a sealed box under the seat of my SLK320 (2001). The electronics are Motorola. Does anyone know what this is? I think it might be the cell phone but I'm not sure. Is it needed?

Yup, you found the module that connects the MB startac to the audio system.

Thanks, any idea if my radio will still work w/o it? I have the bose tape deck with an amp under the passenger side carpet. What about the car? Will it still run w/o this box and will I get any dash lights?