A few weeks ago, I helped a friend look for a wedding dress at the Nordstrom at Santa Monica Place, a swanky outdoor mall located in the iconic Southern California beach city. Having found a summery white dress perfect for her backyard wedding, we approached the cash register, where an enthusiastic young sales associate “rung us up” using the store’s mobile checkout pilot program.“I’ve been waiting all day to do this,” said the young woman, excitedly pointing an iPod equipped with a plug-in device in our direction. She scanned the bar code on the tag of the dress, swiped my friend’s credit card, and emailed the receipt in addition to printing it (wirelessly) at the communal terminal in the center of the showroom.Apple has introduced plenty of consumers to the mobile checkout, but get ready, because it’s coming soon to retailers big and small near you. By all accounts, cas