Have you seen wink toolkit? Similar to sencha touch but with some extra effects...like page flip.
Not sure how well they will play together though as I haven't tried it...
The reason why we haven't implemented these flip like transitions yet is because they won't work on anything other then iOS. Android has some serious issues with css transforms, causing the whole page to flicker and form fields to randomly break. We wanted to provide transitions out of the box that work across all devices. We might add some iOS only plugins later with support for 3d transitions.
I have the same demand.
And found this JQuery-driven flipper: http://builtbywill.com/code/booklet/, it works fine on Android (Gingerbread & Ice-Cream-Sandwich) and iOS5.
But how can I put this together with Sencha? As custom animation? No Idea...