I personally don't like the TSA paying any more attention to me than necessary. I wouldn't risk having to go through extra screening just to keep a MB on my wrist.
A watch is old technology. The fact is we don't know exactly what is in that MB. We know there is RF technology. There is likely other technology in there as well since the bands have the ability to do things the RF cards can't do. I wouldn't try taking a band through one of the screeners no more than I'd try carrying a phone or Bluetooth. It's unnecessarily inviting questions from the TSA.