Touch interpretation?

[Ben Rubinstein]

Being a lazy sort, until now on mobile apps (which are all for internal use, 
not publication) I've just used the standard controls, and at most tracked 
mousedown/mouseup (for convenience of desktop development) to drag something.

However now I'm trying to make a rather more native-like app, and respond to 
swiping in various directions, and two-finger pinches.

So I've started coding simple heuristics for when a touch sequence is a tap, a 
swipe, or a drag; and the next step is to consider when it is actually a 
two-finger gesture.

But obviously the community has been there way before me. Are there any shared 
libraries developed to implement this? Or at least commonly agreed good 
heuristics?

TIA,

Ben