Charging the key.
Can you just leave it in the ignition?
Does the ignition have to be turned on?
Must you be driving for it to charge?

I hope I can just leave one in the ignition and lock the doors with the other key.
Sure would be nice to know the keys have a FULL charge.
How can you tell what state of charge they are in?

Hmm, that is more than one silly question.
I can not figure out how to put all of those into one question.

 

I think it depends on which type of key you have. My '02 came with the standard master key (lock, unlock, oval shaped bow, non-retractable blade), and I don't think it gets recharged while in the ignition, since it just has a regular watch battery.

 

05+ (model year) with an inductivly charged key, gen 1, if i had to bet, needs to be running to charge the key. That having been said, i have left my spare key for 1yr or no, no use, and had it work fine.
I just use the spare for a couple long drives a year, and great....
If the battery dies, just use the key in the lock....

 

MINI suggests switching keys every 6 months to keep them charged.