HvdGChamp
I would like to suggest the addition of a panic button. This button will immediately freeze all cards and disable all connected clients except for the one the user is currently using.
This is useful when you have been robbed or pickpocketed and need to disable all cards urgently. It could also be useful when you have lost your wallet and aren't sure if someone with bad intentions has it in your possession.
Maybe also create a widget so users can place it on their homescreen?