The humble cycle computer has come a long way since I was a kid. There's no end of GPS-enabled pieces of kit with heart rate monitors and watt meters and other handy gadgets. Though I am pretty conscientious about keeping track of my riding data, a simple cycle computer has been quite sufficient for me for the past few years, though I've been tempted by some of the bike mounted GPS units - until I see the price!
I've played with a few iPhone apps of late and have been thoroughly impressed by one in particular. Cyclemeter has all sorts of handy functions I never knew I needed. It tracks and records your ride of course, but also offers simple one-click uploading to Facebook and Twitter, calendar integration and plenty of other impressive features. And if you so desire it will tweet or update your Facebook page at set time or distance intervals and read out the responses from your friends. It auto stops and starts. My favourite feature is the voice announcements (which I have set to alert me every kilometre because I find them so charming) in which an Englishwoman's voice tells you how far and fast you have gone. As a bonus, the app is very economical on the phone's battery, provide you ride with the screen turned off. I tend to leave it in my back jersey pocket, the voice announcements cheerily reminding me that it's still working away.