Besides a larger display and redesigned metal body, details regarding which features the next-generation iPhone models will pack have been light. However, it appears that the new models could include a new sensor: a barometer.
A barometer is a sensor commonly used for measuring altitude and the sensor is already commonly found in Android devices such as the Galaxy Nexus. A barometer sensor could be used by hikers, mountain climbers, bike riders, and enthusiasts who want accurate knowledge into their current altitude. Barometers, via air pressure data, also measure temperature and weather information.
The information regarding the next-generation iPhone likely including this sensor comes via Xcode 6 and iOS 8, the latest iPhone software development kit and operating system. The software includes updated CoreMotion APIs that clearly reference the new altitude measuring capabilities: