Smart watches are fine, but they really don't capture the DIY spirit. Over on Instructables, user benhur.gonvalves shows you how to build a smart little watch using an Arduino that comes packed with a pedometer, temperature reader, compass and more.
You'll need an Arduino Pro Mini, some sensors and a little general PCB knowledge to get it made. The end result is a watch that tracks your steps, checks the temperature and altitude, and works as a compass when you need it. As you'd expect from a prototype, this isn't the most beautiful thing on the planet, but the guts are there so you can customise it to suit your own style.
Arduino Pedometer Watch, With Temperature, Altitude, and Compass [Instructables]