Reading this thread a question comes up to my mind.

If in the future, you can pay with bitcoin almost everywhere, how are you going to pay? The safest way to store your coins is to use a hardware or paper wallet (properly created). But in order to pay for a coffee at the coffee shop you can’t use it, unless you carry your laptop or tablet everywhere.

Using your mobile isn’t safe. At least as safe as using hardware or paper wallets. So, how do you think it will be done? Transferring just small amounts to your mobile? Maybe hardware wallets will have a mobile version?