Nike + iPod question

Hello, I'd like to ask you some questions about the Nike+ sensor.

1. When I enable it in iPhone's sys pref, does it mean that it is always transmitting? What about iPhone's battery?

2. Concerning sensor's battery, it says it goes auto sleep. What about if I keep the switch on (on the iPhone) and I start to move?

3. What about the kind of transmission? Is it a sort of radio?

Thank you