There is a little Android app called simpleaf, a scratchpad including multiple pages, transparency toggle, ereaser ....which in my opinon works very well with SD. The feature I like the most is toggling between transparent & opaque mode. Would make  a nice feature for the SD scratchpad as well.

During flight I have to decide whether I take my SD device right & the kneeboard left, resulting in good SD handling & often illegible output on the left side or crosshanded operations. I would prefer to rest my left hand on the stick & do all the other work using the right, how it is supposed to be. The idea would be to replace my kneeboard on the right thigh with my SD device for taking all the notes during flight. Something which could be easily done by using the integrated scratchpad. Adding some refinements like transparency toggle ....and it would be even more handier.

I wonder if the transparency toggle could be made into something that would allow me to annotate semingly on the chart. That would be handy, too!

-- Chris.