Use Owl Intuition and Raspberry Pi: http://www.raspberrypiusers.com/?p=7484 (Python code) Slides: http://www.slideshare.net/raspberrypiusers/pi-owl-electricity-project-14840495
Other python program: https://code.google.com/p/owl2pvoutputorg/downloads/detail?name=owl2pvoutputorg.py&can=2&q=