[Mouse Gesture] push and move your finger immediatly [iphone] dunno [palm pre] dunno [requires multitouch] no [proposed function] 
z o o m i n
z o o m o u t
f i n g e r s c r o l l i n x / y t o o
z o o m i n a n d o u t
t w o f i n g e r s c r o l l i n g
n o t p o s s i b l e