Apple has launched a new online tool to allow potential iPhone 3GS customers to check on the stock levels at any of the company’s U.S.-based retail stores. Currently, iPhone 3GS availability varies wildly from store-to-store, with some stores sold completely out and some down to just one model available; most of the company’s biggest stores, such as The Grove in LA, the downtown San Francisco store, and the company’s glass cube 5th…
