One of the most intriguing launches at Interbike was a pairing of power measuring crank spider and power meter/global positioning system (GPS)/heart rate monitor/altimeter computer from new company Quarq Technology. What's especially interesting if you're a hardcore bike instrumentation geek is that the display unit will run open-source software, so developers will be able to modify it and write applications for it.
http://www.bikeradar.com/news/article/interbike-quarq-power-meter-real-bike-computer-12672