It was a wise decision that I waited until 3rd generation of iPhone is out. It was a purchasing decision of no real technical reasons. I needed my iPhone for music, to run using Nike+ besides I need a phone in case of emergency while I run. I should have waited 4 more months for the iPhone 3GS instead of spending the money for a iPod Touch 2nd Gen.
Last year you'll have to buy the iPod transmitter + sensor kit. The sensor alone was available to the US market at US$10, now it's US$19. I guess since the iPhone 3GS launch Apple has started making sensor available from their online store to all markets with 3GS, now it's HK$150 for just the sensor.
My sensor did 370k with me and lasted for nearly 11 months, that isn't too bad. However the sensor failed just 40 meters before my set distance target of 5k yesterday. I had to reboot my iPhone and found no run history saved, too bad.