probably this theme have been discussed in the past, but...
I use to have an Android tablet and find it very useful also as a kifu.
My favorite APP is BW_GO, by Marc Oldenhof, mostly for
1. easy to access window and controls
2. very useful tool for replacing a stone if in wrong position (that's a MUST with tiny screens and BIG fingers)
The only thing that I miss is a proper Go-Clock (very helpful to understand one's game mistakes and indecisions during the analysis/review).
Also, I would like to have a specific tool for sgf paper diagrams (e.g. tsume go for validating a solution).
Do you use a specific APP?
Please share and advice.
Galation