Let's Do Spelling From Andrew Brodie!
The apps are all tailored to the English Curriculum and has plenty of activities to help children develop their spelling.
I really like the audio element and how each word is put into a sentence and read aloud before the student then spells the word.
The app uses the tried and test 'learn, write, check' approach in the practice section and each activity has three levels of difficulty. For a quick demo of some of the features, check out the video below: