A case for electronic devices that can be converted to a wrist-wearable mount with very little effort. In a first position, a flexible strap serves as a case for a hand-held electronic device. In a second position, the same flexible strap serves as an arm-attachment mechanism, whereby the hand-held electronic device can be worn on the user's arm. A swiveling base is provided so that the hand-held device can swivel in place while being worn. The mechanism may be used to mount a variety of electronic devices, including PDA's or other flat-panel display monitors, keypads, bar-code scanners, magnetic storage medium readers, GPS receivers, microphones, speakers, and other devices.