'The Pinball Arcade' have a great touch input system, this works as follows...
They have 5 direction nudging, and also adjustable touch nudging zones ie different scheme's the user can select which control what areas of the screen do what and what size the touch zones are.
They also have a toggle which allows a touch zone to be graphically visible during play via a translucent boundary box.
Scheme A - with zone visibility switched on.
This has 3 areas on the bottom row which are Left Flip / Nudge up / Right flip.
The middle row has 4 zones -Left Nudge / Up Left nudge / Up right nudge / Right Nudge.
The zone visibility toggle is on in this clip, and the boundary zones are identified with translucent frame as can be seen.
Or Scheme E - with zone visibility switched on.
Same zones as Scheme A but the flipper area is smaller vertically meaning your thumbs have less distance to move for nudging - great for tablets.
There are 5 different scheme's currently.
This makes a massive difference to control of play using touchscreen inputs.
Any chance you could shamelessly copy this for Android?