Chums has long been making unheralded but important accessories designed to keep accessories like sunglasses and watches safe and on your person during all the most vigorous outdoor activities. I recognize the name most for their line of sunglass retension straps that wrap around your head and keep your glasses from plunging off a cliff or into the river.
I'm also pretty familiar with The Band, though I'll admit I didn't know Chums made it. Basically a Velcro strap designed to swap out with your watch band to make it better-fitting and more sports friendly, The Band is a pretty readily available accessory that you can find at a variety of sports retailers.
After Apple announced its all-new, touchscreen-based iPod Nano in September, Chums repurposed The Band specifically for the device. You can turn your iPod Nano into a high-tech watch/wristtop music player with the help of its wide-version band. It doesn't look like they even had to do anything to The Band to make it Nano compatible--outside of advertising. You're welcome, Chums.
The Bands come in a variety of patterns and retail for seven or eight bucks. In case you need help figuring out how to make your Nano watch, there's an instructional below. But really it's as simple as clip it and strap it. Just don't display with your hand on your hip like that guy in the picture--that's just fruity. You can buy Chums The Bands here.