Future iOS and watchOS devices could sport advanced environmental sensors, as evidenced by a newly granted Apple patent (number 9,804,003). These could include a temperature sensor, a pressure sensor, a humidity sensor, a gas sensor, or other sensors or combinations of sensors for sensing attributes of the environment surrounding the device.
The sensor components may be mounted within an enclosure that at least partially surrounds the sensor components. The enclosure may have an opening that allows sound and/or other environmental materials such as air to enter the enclosure and interact with the sensor components.
The sensors could be used in a variety of ways. An iPhone, iPad or Apple Watch could alert you when smoke or carbon dioxide is detected, posing a safety issue. Ambient pressure measurements may be used to adjust the way in which microphone measurements are made (e.g., to accommodate audio characteristics that change with changes in altitude).
Of course, Apple files for — and is granted — lots of patents by the U.S. Patent & Trademark Office. Many are for inventions that never see the light of day. However, you never can tell which ones will materialize in a real product.