It doesn't appear to be available on android.
Looking at the blurb and the Self-evaluation, I think I can see where they're going with it. Teaching reading and spelling of the HFW through decoding, blending and grouping words with similar 'tricky' graphemes is not a bad idea, and is probably better than most of the apps out there that try to teach HFW.
What I've read does seem to show some issues with the subject knowledge of whoever wrote it. The use of the term 'silent letters' isn't great. And it gets worse with the examples given in the self evaluation. The first 'h' in 'which' isn't silent (or at least it's as silent as all the other letters), it's part of a digraph that is used to represent the sound /w/.
The 'tricky letters' (not sure I like this term) identified in the words 'want, mother, coming, can't, magic' aren't all that tricky. They are all fairly common. They are identified as tricky in L&S because that particular scheme introduces them at a stage where those correspondences haven't been taught. They may not be tricky words in another scheme.
Difficult to know how far those two things affect the app without seeing it.
Not sure about the monster colour thing. might be a good hook for some children. I'd want to be sure that it didn't detract from actually looking at letters and end up with children who could manage the app but couldn't transfer that to other reading where there weren't colours/monsters etc.