Wired gives us a look at a number of bicycle-related applications for the iPhone, including Back Light, which allows you to tell cars following too closely on your back wheel exactly what you think they should do with themselves ("Stop!," of course). I'll admit I would put a lot of other choice statements there, but that's because I'm not as sensible as you, dear readers.
Another app, Brake Lights, which accomplishes essentially the same thing but won't get you in as much trouble with someone behind the wheel of a three-ton vehicle, is a simple brake light activated when the phone's accelerometer senses your movement slowing. Likewise, there are several apps that intend to mimic your blinky, but I'm pretty sure nothing could get as shockingly bright as a Planet Bike Superflash (do not hold that up to your face and look into it, please).
For the fixie kids, there's an app that helps you figure out the ratio for your gears and shows you where on your tire all the skid-stops are going to wear it thin. It also lets you know how fast you're going to travel at different RPMs, depending on your tire size. A bit arcane for me, but obviously there are folks who find this interesting.
One of the apps that didn't make Wired's list, iMapMyRide, tells you your speed and distances traveled, and allows you to map your rides and keep a record of them both on the hand-held device and online.
We're curious to know what other apps out there that you find useful or interesting? Let us know in the comments.