Abstract: An input device provides input to a portable electronic device. The device detects movement of a user's fingers on an inert work surface, and transmits signals representing the detected input to the electronic device. The input device can take any of several forms, including a cradle or protective cover that attaches to the electronic device, or a separate unit that transmits signals to the electronic device via a wired connection or wireless connection. In an embodiment, techniques are employed to properly position the input device despite user adjustment to the position of the electronic device. In an embodiment, further techniques are employed to maximize the stability of the input device and to protect its components from damage.