We hope you didn't just get some business cards printed, because you're going to want a new set. Square already simplified card payments with its phone-based swipe widget, and allowed businesses to take money through its Cash app. Now, it's introducing another way to fill (digital) wallets: "$Cashtags." Choose your own tag ($jondoe for example) and then anyone who wants to throw some money your way can just go to https://cash.me/$jondoe and securely wire you the green. Square has also just opened the Cash app to all US businesses (with a 1.5 percent transaction charge).