The promise: Determines which credit card is best.
Available on: iPhone, Android
If you have multiple cards -- and especially if some have awards that change frequently or give extra points at, say, gas stations -- this app will help you use them strategically.
Choose a merchant, and the program calculates which of your cards will give you the best deal (it may also show you a related ad).
Even rewards junkies sometimes use the wrong card, says Randy Peterson, a frequent-flier expert at InsideFlyer.com: "Wallaby gets rid of the guesswork."
If there's an extra $10,000 in your budget, consider investing in low-cost index funds, buying a reliable used car or taking a European river cruise.