It's a pretty common thing to see in an online store: pay with PayPal -- but what about on mobile devices? Well, the eBay-owned company is working on that. The company just announced PayPal One Touch, a new system that (as the name implies) hopes to make paying of items in mobile apps a one-touch affair. The feature isn't an app itself, but rather a service that can be embedded in other apps. Users will log into their PayPal account one time, and subsequently be able to pay for products in supported apps with a single click.