Square (www.squareup.com) has been an interesting company to follow. Founded by Jack Dorsey, they specialize in seamless mobile transactions, via iDevice (iPhone, iPad, etc.).
Today they released CardCase, a dramatically landscape shifting application. CardCase makes mobile payment seamless for the buyer (I imagine a parent juggling three kids without having to dig into a wallet/purse for a credit card), but, I see bigger growth and traction for vendors, who will have detailed (and realtime) tracking of their clientele. Vendors will be able to develop tailored merchandising metrics (based on users, purchase times, etc.) to cater to loyal patrons and entice potential buyers within their vicinity.
As an added bonus, CardCase is aesthetically sound. Once Square spells out its privacy restrictions (to allay user trepidation) I would expect exponential growth.
Job well done.