A method of operating a communications system including a mobile phone and a media playback device is disclosed. When the mobile phone is uncoupled from the media playback device, voice telephony services are provided by the mobile phone using an onboard RF transceiver of the mobile phone. When the media playback device is uncoupled from mobile phone, media playback services are provided by the media playback device using an onboard CODEC and an onboard display screen of the media playback device. When the media playback device and the mobile phone are operatively coupled together to form a tandem device, video telephony services are provided by the tandem device using the RF transceiver of the mobile phone, the CODEC of the media playback device and the display screen of the media playback device. Methods of operating a GPS system including a screenless GPS device and a mobile phone are also disclosed herein.