The industry has not shrunk celullar phones more because they cannot shrink our fingers to manipulate more reduction. Screen typing can be %^#$@! if you are over 11.
Seen on the web guys making capacitive/conductive styli instead of buying, for the kick of it, using conductive foam.

How do they make it work ? If a piece of conductive foam performs, why a metal rod does not ? Or a pencil lead in contact with the hand ?

I tried two types of conductive foam borrowed from my ICs matresses. A soft one that is crumbling/dissolving works. A shinier/stiffer one does not.
Or is there something about how many mm area is the surface touched in order to respond ?

 

Found something very interesting...
Holding a plain vulgar metal rusty nail on the hand, (not a finger nail), the touchscreen does not respond to its tip. It responds fine tapping the touchscreen with the nail head. So surface contact area is relevant. As in a capacitor...

 

Yes, the surface area is important since it is a major factor in the amount of capacitance between the finger or stylis and the screen.