I have glimpsed the future - and it looks a lot like free hot chocolate.

Late last month, I ordered the beverage at Sightglass Coffee in SoMa, grabbed it from the counter and walked out without cracking my wallet.

Nobody chased me down because, when I first approached the cafe, the Card Case app on my iPhone detected the store's perimeter and automatically switched on. It broadcast my picture to the barista, who could then tap my pre-entered credit card number to cover the bill. The phone never had to leave my pocket.