Sleeves for different portable electronic devices (portable media players, wireless telephones, handheld computers, etc.) adapt the outer contours of the devices such that all can fit within the pocket of a standard device dock. Each sleeve situates its portable electronic device within the pocket of the dock such that at least one of its power / communications ports is situated at a standard location. The device dock then also accommodates a connector which fits within the dock pocket, and which has power / communications ports situated at the standard location, such that when the sleeved device is inserted into the pocket, its power / communications ports interface with the power / communications ports of the connector. The connector can incorporate data storage devices, power supplies, interface cables extending to other devices (such as personal computers, stereo systems, etc.) such that it lends the functionality of these devices to the sleeved device situated within the pocket.