iPod sport kit
It sounds neat in many ways, and I like the way there's more and more embedded electronics in modern sports kit. The review doesn't really say anything about the accuracy of the sensor with respect to speed and distance. But the sensor is really small and doesn't need specific Nike+ shoes to work, just tape it to any shoe you like. I guess the accuracy is quite good and about the same as the Polar S1 foot pod, with the same sensitivity to the surface, because it measures both the accelleration of the foot and the frequency of foot strikes. The only other way I know of is GPS, but a GPS receiver needs relatively open skies and it's vulnerable to interference from buildings and doesn't update nearly often enough to show the correct distance if you run a very meandering course.
Besides, all these gadgets from different manufactures should learn to talk to each other, and ANT seems to be an attempt at some standardization in the area. It does seem it's mostly just Garmin using it for now, everybody else is doing their own thing or, if it's a device with heart rate monitor, using the Polar sensor/sender chest strap; SRM and Ergomo spring to mind.
I've started to run again today, trying to learn to run correctly via the Pose Method of Running, so I've gone in the other direction to get rid of distractions, running with just my watch and concentrating on correct technique in my new minimalist shoes. It was really nice getting back to basics like that, but I will eventually get back to my high-tech S625x in 1–2 months' time — when I've more or less learned to run correctly.