I'm using Patternly a lot now, and it is very helpful in writing patterns while you knit. No more lost or incomprehensive writen notes! And I always have my notes with me, which is also very handy.
(Original app pic from Patternly)
One downside of Patternly is that it is not possible to edit a row for the pattern after you clicked "add row", or maybe I just haven't found that option yet.
I'm going to stroll the Google Play store a little more to find some more interesting knitting tools.