Open Hotel Alert makes sure you get a spot in your preferred hotel on your next holiday, convention or other trip -- even if it's sold out when you try to book. Just tell it where you'd like to stay and when, and if the hotel is sold out now, it will text or email you when something opens up. The service doesn't do anything you probably couldn't do if you didn't want to sink the time in -- it just checks room availability frequently for the hotel you select, and lets you know if something opens up by text or email the moment it does. You could set an alarm to check every few hours yourself, but the whole point of the service is so you don't have to.
Since you get an alert as soon as something is available, you're in a position to book that room right away, and the app will give you a direct link to book to jump out and book the room (which, by the way, is how Open Hotel Alert makes money -- through Booking.com's affiliate program). Hit the link below to give it a try.