Fair enough, I may not be able to get my hands on the Nike+ system unless I purchase a pair of Nike running shoes — which totally irks me — but for only $10, I can get something that can help me during my runs, without compromising my favorite footwear.
RunKeeper is a new app for the iPhone that uses built-in GPS on the 3G models that helps runners, walkers, or cyclists monitor their route and distance throughout a city. So far it sounds like it is fairly accurate and is said to work better than Nike+ iPod's pedometer estimation tools. And best of all, once you get home you can check out your route, distance, and pace on Google Maps!
You can download the RunKeeper from Apple's iPhone App Store.