Apple Watch’s NFC band technology
The Apple Watch can then identify which band is connected, then use that information to do a few different things.
For instance, watchOS could dynamically change its user interface based on which band is attached. This could include changing watch faces altogether or adjusting the design of the current watch face to better match the color of the new watch band. The Apple Watch could also toggle different apps, such as the workouts app, when a particular band is connected.
Additionally, this could also allow Apple to crack down on third-party Apple Watch bands. The report from Patently Apple highlights this text from the patent:
Upon determination that a band that is coupled to the device is not an authorized band, a warning may be provided using an output component of the device, and/or one or more features of the device may be disabled or otherwise modified. In another example, a particular band may be associated with a particular application or service on the wearable electronic device.
Upon identification of a band that is associated with a particular application or service on the wearable electronic device, the device may activate or provide access to features associated with that application or service
The patent also describes a system in which the Apple Watch bands include other components alongside the NFC chip. This could include “one or more sensors” such as “environmental sensors, biometric sensors, gesture sensors, inertial sensors, or the like.”