Mobile payment--so recently novel, now ubiquitous--is getting better fast. Most significant, the services are increasingly targeted. You manage your accounts through QuickBooks? There's a service precisely for you. Your customers use mobile wallets rather than credit cards? You have choices.

In this graphic, the first six options are mobile versions of conventional point-of-sale systems. They come equipped with card readers--dongles--and proprietary apps. The next five options have nothing to do with readers. They are all about the app, on both sides of the transaction: Your customer pays not with a card but with a phone. So these products function less as virtual cash registers than as ways to beef up your brand by adding convenience, word of mouth, and app integration.