There seem to be a ton of them that work with iPhones but after searching around I can't seem to find anything that will work with an Android.

I'm running a Nexus 4 with the latest release of KitKat. It has Bluetooth 4.0 compatibility. Battery life is not a problem with a battery pack in my handlebar bag and also with having a hub dyno and a USB power converter. Having route guidance (visual and voice turn-by-turn) as well the ability to run my own maps and ride directions on a big readable screen on a piece of equipment I already have and will be bringing along anyhow is the future IMHO.

Currently I'm using a Zephyr HxM Bluetooth wireless heartrate sensor and it works great with Android and plays nice with Endomondo. But it seems that if I want to record cadence information I either have to go back to a dumb Garmin or other ANT+ system or drink the Jobs Kool-aid -neither of which I'm willing to do. I really like having all the features of a smartphone as my cycle computer but would like to add something as simple as a cadence sensor. So far there seems to be nothing. Topeak seems to say their unit will someday have Android functionality but so far, nothing...