I\'m using JQuery with a mobile site to reposition the header nav on scroll in the absence of position:fixed support. That works fine, when the user stops scrolling the head
You can start with jQuery Touchwipe : it's a plugin which add new events, wipeleft and wiperight.
It can be easily modified to change horizontal wipes to vertical ones (changing x's to y's)
http://plugins.jquery.com/project/Touchwipe-iPhone-iPad-wipe-gesture