eBay's (NASDAQ:EBAY) mobile efforts extend to building apps and developing in-store mobile promotions for bricks-and-mortar retailers such as Macy's (NYSE:M) and Toys 'R' Us, via its GSI Commerce unit. Though eBay competes with regular retailers, GSI's mobile solutions give the company a chance to profit from transactions that would happen offline anyway. There could also be synergies with PayPal, which is quickly expanding its offline presence. (more on eBay/mobile: I, II, III)