DS liked the Hairy Phonics apps - we got 3 in the end:
Hairy Phonics 1: sh, ch, th, ck, ff, ll, ss, zz, ng.
2: ai, ay, ee, ea, ie, oa, oi, oy, oo
3: ar, or, er, ir, ur, a-e, o-e, i-e, o-e, u-e.
They have little animations using the sound, then you draw the letters with your finger, then a game that practices words with that phoneme, so it rehearses each one a bit more than TYMTR (which DS also played and liked).