Consumer advocate and credit card expert Beverly Harzog of Atlanta has another concern. If the app is used to determine which card to use to maximize rewards, that's fine, she says, "But I worry it might encourage excess spending because of the rewards involved."Getting 5 percent cash back is a nice bonus, but only if it's something you really need to buy anyway. Five percent of a $250 item ($12.50) you didn't need or will regret buying later isn't going to get you very far and you're still out $237.50. Will using Glyph help you make the most of your rewards and cash back credit cards? It might be nice to have one less thing to keep track of in the world and let the app make the best call. But if you're like me, happy to monitor my credit card programs, then Glyph probably won't tell you anything you don't already know.