I am asking to learn. If I have to use this card, do I also have to have my cell phone with me all the time? If I go downstairs to get a Bagel in the morning,

I am asking to learn. If I have to use this card, do I also have to have my cell phone with me all the time? If I go downstairs to get a Bagel in the morning, I need to take my phone, or else no Bagel for me? And it seems from the "Iphone will alert you using Bluetooth" facility, that I need to have Bluetooth on all the time, which I normally do not, to save battery life (adds an hour or so on my Iphone4). To me this is a functional gridlock. Does it also need to be connected to some data network or the other to work? If I lose this Coin card, then is it same as losing all my cards? If my assumption is true that this needs to be paired with a phone always, then will it not be possible to nullify the card, using the app on the phone, in case I lose the Coin card? Thanks