I found this app while I was checking free apps on itunes. It is focused on helping students learn to order numbers of all types. When you open the app you have a choice of full course (levels 1-14) or the advanced course (levels 8-14). Each level focuses on specific numbers such as naturals, integers, fractions, decimals, absolute values, and square roots. When you play the game, it will automatically start at the lowest level. It shows 5 cards with 5 numbers which the players has to tap in order from lowest to highest. If you select the correct card in the correct order, it will fly off the page. If you are incorrect, it will not move, so you have to make a different choice. There are only 5 cards in each level so you would not get a chance to really practice with additional cards.
Although I like the idea, I am not sure I would use this in my classroom as it does not provide enough real practice in ordering numbers. Many of my students would just touch the cards until they get all the cards off the screen before moving on. There does not seem to be a mechanism in the app to have students practice different numbers until they are proficient at ordering them.
The only way I see using this is to let students practice a level on the app and then do a worksheet asking them to order the same type of number.