This is a breakout board for the Bosch BMP085 high-precision, low-power digital barometer. The BMP085 offers a measuring range of 300 to 1100 hPa with an accuracy down to 0.03 hPa in ultra-high resolution mode (that's 0.25m of altitude at sea level!) It's based on piezo-resistive technology for high accuracy, ruggedness and long term stability. These come factory-calibrated, with the calibration coefficients already stored in ROM. Writing your own code for it requires some math, but there are plenty of examples and libraries available (see below). Project description, more information and ordering can be found at https://www.sparkfun.com/products/11282 Datasheet: http://dlnmh9ip6v2uc.cloudfront.net/datasheets/Sensors/Pressure/BST-BMP085-DS000-06.pdf Quickstart Guide: http://www.sparkfun.com/tutorials/253 Example Arduino Sketch: http://www.sparkfun.com/tutorial/Barometric/BMP085_Example_Code.pde Example Code: http://www.sparkfun.com/datasheets/Sensors/Pressure/BMP085 Example Code.zip Product Flyer: http://www.sparkfun.com/datasheets/Components/General/BMP085_Flyer_Rev.0.2_March2008.pdf Wiring Example: http://wiring.org.co/learning/libraries/bmp085.html mbed User Review: http://mbed.org/users/tkreyche/notebook/bmp085-pressure-sensor/ Bildr Tutorial: http://bildr.org/2011/06/bmp085-arduino/ Pressure units converter: http://www.sensorsone.co.uk/pressure-units-conversion.html