A battery pack is provided for a mobile communication device, comprising a casing defining a cavity that conforms, at least partially, to the outer shape of the mobile communication device and one or more rechargeable power cells housed within the thickness of the casing. An internal interface engages a corresponding interface on the mobile communication device to provide power from the one or more rechargeable cells to the mobile communication device. An external interface is electrically coupled to the internal interface in order to transmit signals from the mobile communication device to an external device and may further serve to recharge the one or more rechargeable power cells. The battery pack may also serve as an extendible platform by providing additional integrated communication interfaces and/or processors that can be utilized by the mobile communication device to extend its communication and/or processing capabilities.