Well if the coin can be deactivated when it's out of range, that would mean the coin has to be "smart" because it wouldn't be the phone app doing the deactivation but the coin itself. In that case, why couldn't the coin take extreme measures and just wipe its memory? Inconvenient for legitimate situations where the card is out of range and not accidental ones, but I imagine it's quick process to reload the coin with your card(s) data.