I came across this app when it became a free app of the day (it's still free). It's a lovely little app with lots of ELT potential. At first look it reminded of the software that comes with IWB as it has the potential to do the same sorts of things in terms of exercise creation. However it has the advantage over the board in terms of portability. As students can also download it, it also has the advantage of handing over creation to the them.
It works by creating 'projects'. In simple terms a project is created by using text and images. Once created, a project is saved on your device so you can access it anytime. You can also share it by email. The app also comes with access to the a drop folder where there are lot of already created projects for you to download. Many of these would supplement the ELT classroom.
Here is a screenshot of me playing with a project.
(note photos are from http://www.flickr.com/photos/eltpics/sets/72157625304912259/)
As you can see, you can choose a background for the project and then by tapping on the screen you create a text box. You can choose the colour of the text board, decide the size of the text or even add a photo. You can also clone any box over and over. In the example you can see how I have used text boxes to create a sentence. So one possible way this can app can be used it is to create 'put the sentence' in the right order tasks. In the lower part of the screen I have added three photos to show how you can use the app for drag and drop (well, move and match) vocabulary exercise.
It would also be very easy to make activities such as gap fill - create a sentence with a gap on one text box and then create options to fill the gap in other boxes. Thus using move and match to fill the gap. Another exercise type, though a little time consuming is categorisation, as shown by this image taken from the move and match dropbox on food.
The app is quite versatile so can be used for everything from grammar exercises through to vocabulary practice, either prepared by you or given to students as a project that they can then share with their classmates.