I am considering turning on the tethering option. I want to be able to use my laptop while at work, connected pretty much all day for IM and email. If I have the tetherig turned on on the iPhone, can I stay connected to it without burning through my data plan? How does that work, does it only use up data when you're actively sending and receiving things? Or if it's tethered to a laptop, will it constantly be sending and receiving anyways since there's things that constantly get very small streams of data, like an IM client or gmail checker? Also, can the phone be locked and still stay tethered all day, so it could be in my pocket or sitting on the desk and still work? What does the tethering setup look like on the laptop, will I just see a new wifi network that I connect to?