The MPL3115A2 is a low-power, high-precision barometric pressure sensor. The sensor can be used to detect changes in barometric pressure (weather changes) or altitude (UAV controllers and the like). The sensor is very sensitive and can detect a change of only 0,05 kPa, which is equivalent to a change in altitude of 0,3 m.

The sensor interface is I2C and can measure temperature as well as pressure. 

Specifications:
Operating voltage: 2.5 - 5V
Interface: I2C
Measurement: Temperature, pressure (with high accuracy also for altitude measurement)
Typical pressure accuracy ±0,05 kPa
Typical altitude accuracy ±0,3 m
Typical temperature accuracy ±3C