City of Santa Monica has been installing video detectors on the top of traffic lights to detect bicycles. They've painted markings where bikes should stop so they can trigger detection. I've found that these work pretty well. Some streets where the loop detectors previously never picked up bikes (even when positioned at recommended spots for the type of loops) now change signals fairly quickly.

http://www.smmirror.com/#mode=single&view=33719
http://la.streetsblog.org/2011/12/02...-santa-monica/