The estimating system of extreme programming is based on XpVelocity and YesterdaysWeather. Inherent in this is the idea that when you make estimates, the actual units you estimate aren’t important – what’s important is you estimate by rough comparative value and use YesterdaysWeather for calibration.
For the last year I loyally biked the 1.3 miles to and from work, but since I got a pedometer I’ve been walking 80% of the time. It adds an additional 15 minutes to my commute time each way, but the big bonus is it allows me to listen to my favorite podcasts. I’ve compiled a list of the podcasts in heavy rotation on my walk of walks here.