It's a third party app that checks availability. Unlike the previous third party website that did this (using the website developers dvcmember log on), this app requires you to enter your member website log on information in order to work.
I don't see the advantage of this app now that there is the resort availability tool on the DVC member site. I don't like the idea of giving our my DVC user name and password to a third party.
Has the app an alert function? If it scans the website to check if the room you want is suddenly available it can be very useful. It would avoid manual stalking of the website.