Wearable electronic devices can include connection mechanisms for adjustable and exchangeable connections with selected modules other devices to enhance performance of the wearable electronic device. Such connections can provide both mechanical engagement and operable communication between the connected devices. Arms, earpieces, accessory devices, and/or other external devices can be easily connected to provide different components and functions at different times as desired. Accordingly, a main portion of the wearable electronic device need not include permanent components that provide every function that will later be desired by the user. Instead, the wearable electronic device can have expanded and customizable capabilities by the use of one or more arms, earpieces, accessory devices, and/or other external devices.