I am taking my car in on Wednesday for its first "check-up" - when i called to schedule the appointment, the SA told me that they would use my key to tell them what needed to be done. I will see if they can give me a run down of all the info it collects. I will report back! I will confirm if we need tinfoil hats for our cars or not
I do know that when you use the key in the slot, it records all of the dashboard settings you set while using that key. If you have a second key and a second driver, and you are both extremely particular about how things are set up, you can have different settings!
And yes, the battery is re-charged when you use it in the slot, so again if you have a second key, you need to use it every six months or so to keep that battery charged too.