It would connect to another portable device via Bluetooth or WiFi, and would transmit real time information from that device.
As far as how the attachment works, the patent explains:
The most recent widespread use of such a device was the slap bracelet, also called the slap wrap. The slap bracelet consists of layered flexible steel bands sealed within a fabric cover. Typical slap bracelets are roughly one inch in width by nine inches in length. In a first equilibrium position they can be flat. The second equilibrium is typically reached by slapping the flat embodiment across the wrist, at which point the bracelet curls around the wrist and stays relatively secure in a roughly circular position.
So to sum up, it’s like one of those slap bracelets that often get handed out for free during various promotions, except with an incredibly advanced flexible display built in.
The patent application also mentions how one could use the device:
With a touch screen user input a user can accomplish a number of different tasks including adjusting the order of a current playlist, and reviewing a list of recent phone calls. A response to a current text message can even be managed given a simple virtual keyboard configuration across the face of the flexible display.
AppleInsider also adds that the screen would auto adjust depending on your wrist size, so if part of the screen were to be covered up when wrapped around your wrist, it would automatically turn off. Gyros and accelerometers would also help to orientate the information correctly towards the user.
It definitely sounds like a solid device, however who knows exactly when or even if it will be released. We’ll have to wait and see, but I imagine not for a while.