iOS/Android: Most hotels have standard check-in and check-out times. These hours can be frustrating to work around if you're on a red-eye and you get to a city really early. As You Stay is a free app that works with hotels so that you can book for hours at a time.
Let's say, for example, your flight to Boston arrives at 5AM but the hotel you're looking at doesn't allow check-in until 3PM. Typically, you'd either pay for the previous day so you can check-in, which is a waste of money, or you'd just hang around for the entire day until you're able to check into your room. As You Stay aims to fix this problem by booking rooms by the hour. Rates are priced according to the number of hours of your stay, so you're not limited to the hotel's standard check-in and check-out times.
The app's interface is similar to HotelTonight. You select your destination, travel dates and time frame, and the app retrieves a handful of hotels that can accommodate you, along with the total cost. When you tap on a hotel, you'll get details on amenities and maps.
It's also similar to HotelTonight in that it works with hotels with unused inventory. Hotels aren't filling those rooms anyway, so they're willing to flex the hours to accommodate guests. As The Points Guy points out, most of these hotels are smaller boutique hotels, but there are a few larger chains like Hilton and Marriott, too.
To try the app out for yourself, head to the links below.
As You Stay [Apple Store]
As You Stay [Google Play]