Here's how Hopper works. When you're getting ready to book a trip, you tell the app exactly what you're looking for during your travel: when you'll be going, your destination, what kind of hotel you want to stay at, if you want pool access -- those kinds of things. Hopper will start to learn your preferences and recommend places that fit your needs. Once you spot a place you want to stay, "watch" the hotel and Hopper will provide notifications when the price drops and its time to book. The company claims they can save users up to $90 per night on their stay.

Hopper also offers predictions for flight prices, which is primarily how the company built up its significant user base of travelers. The company claims predictive tools can calculate future flight prices with 95 percent recommendation accuracy. Hopper says it saved people more than $2 billion since its launch, so it can probably help you shave a couple bucks off your next trip.