Apple's iPhone 6 may come with a selection of sensors for reading the environment around it. These include pressure, temperature and humidity sensors.
According to electronics analyst Sun Chang Xu these sensors will arrive on the iPhone 6 as Apple "catch[es] up in the sensor department".
According to G for Games the pressure sensor mentioned isn't for strapping on your arm but rather for atmospheric pressure. This makes sense as there are already body-monitoring sensor accessories that can be added to the iPhone as extras. To build these sensors into the handset would encroach on Apple's third-party accessory market, which it doesn't tend to do. The iPhone 5C case being a recent exception.
But this doesn't mean Apple isn't going to include body sensors on a certain wrist-worn device - the iWatch. Xu previously claimed the watch could feature "optical sensors" that measure heart rate and oxygen levels. This makes sense after Samsung has already added optical heart rate sensors into its Gear 2 and Gear Fit wrist-worn devices.
Other rumours that support Apple's use of more sensors include talk of an iOS 8 Healthbook app. There is also word of Apple hiring new people who specialise in health sensors.