In physical computing it's sometimes nice to know how physically close you are to an object. In other words, you may need to know your 'proximity' to an object, that's where the VCNL4000 does its magic. Okay, it's not actually magic, it's a combination ambient light sensor and IR proximity sensor. Project description, more information and ordering can be found at https://www.sparkfun.com/products/10901 Datasheet: http://dlnmh9ip6v2uc.cloudfront.net/datasheets/BreakoutBoards/vcnl4000.pdf Application Notes: http://dlnmh9ip6v2uc.cloudfront.net/datasheets/BreakoutBoards/vcnl4000App.pdf Example Code: http://dlnmh9ip6v2uc.cloudfront.net/datasheets/BreakoutBoards/VCNL4000_Example.pde Bildr Tutorial: http://bildr.org/2012/11/vcnl4000-arduino/