Bosch has stepped up their game with their new BMP280 sensor, an environmental sensor with temperature, barometric pressure that is the next generation upgrade to the BMP085/BMP180/BMP183. This sensor is great for all sorts of weather sensing and can even be used in both I2C and SPI!
    This precision sensor from Bosch is the best low-cost, precision sensing solution for measuring barometric pressure with ±1 hPa absolute accuracy, and temperature with ±1.0°C accuracy. Because pressure changes with altitude, and the pressure measurements are so good, you can also use it as an altimeter with ±1 meter accuracy
 

Typical application：

Enhancement of GPS navigation
    e.g.time-to-first-fix improvement，dead-reckoning，slope detection
    Indoor navigation（floor detection，elevator detection）
    Outdoor navigation，leisure and sports applications
    Weather forecast
    Health care application（e.g. sirometry）
    Vertical velocity indication（e.g. risk/sink speed）
    Target devices
    Handsets such as mobile phones ,table PCs,GPS devices
    Navigation systems
    Portable health caredevices
    Home weather stations
    Flying toys
    Watches
    PCB size:(L*W)1.52* 1.20cm/0.60"*0.47"