This whole 'mobile wallet' thing is starting to appeal to me. When we were in Japan, Nick and I had to fumble with charging up subway cards to get around (and I still have like ¥600 on one that's going to go to waste), while Jean just swiped his phone over a little sensor and charged it to his account. Definite appeal.
Now a cab company in Watertown, Mass. is trying something similar (while we wait for a proper electronic wallet here in the US). They've installed a server from a company called MobileLime at their shop that lets you make a phone call, press a couple of buttons, and give the cab driver the last four digits of your phone number. The price of the taxi ride will then be pushed to your bill.
I already live by debit card, but it's frustrating that so many places still don't take them. Cash is okay, I guess, but another method of quick transactions would be great.