I recently acquired a BMP180 barometric pressure sensor and was pleased to see that it used the BMP085 library from Adafruit, what I was interested in was how accurate the altitude reading was.
The BMP180 is the function compatible successor of the BMP085, a new generation of high precision digital pressure sensors for consumer applications. The ultra-low power, low voltage electronics of the BMP180 is optimized for use in mobile phones, PDAs, GPS navigation devices and outdoor equipment.
With a low altitude noise of merely 0.25m at fast conversion time, the BMP180 offers superior performance. The I2C interface allows for easy system integration with a microcontroller
This is a picture of the breakout I used