Patently Apple:

Although the invention could apply to a wide range of future products such protective covers, advanced versions of Apple’s Smart Keyboard, clothing, furniture, wearable electronic devices, and other items using fabric, the focus for this invention is a future smart fabric Apple Watch band.

And:

According to Apple’s invention, a fabric-based item may include fabric formed from intertwined strands of material with embedded circuitry.

And:

The circuitry in the fabric-based item may gather input from a user and from the user’s surroundings. The circuitry may supply visual output, audio output, tactile output, and/or other output.

And:

In the I/O segment of system 8 may include Sensors such as temperature sensors, pressure sensors, force sensors, gas sensors (e.g., carbon monoxide sensors), particulate sensors, moisture sensors, light sensors, magnetic sensors, capacitive sensors (e.g., sensors for touch or proximity measurements), gesture sensors, image sensors, proximity sensors, touch sensors, button sensors (e.g., switches coupled to movable button members or button regions),

This is a fascinating, far reaching patent.