I've been working on an example app (for iPad) that is a much-simplified version of Graffle. However, so far it doesn't have resize handles. It's more focused on getting all of the gesture recognizers working together -- selecting, moving, panning, zooming, rotating, nudging, etc. We'll add this example project to the frameworks soon.
Once you have gestures set up, handles are just a matter of hit-testing (did the user start the gesture on a handle?). You can do the calculation yourself or use subviews with userInteractionEnabled=YES. You should try to maintain a 40px by 40px tappable target area for each handle, even though the handle graphics will most likely be a lot smaller than that.
As far as I know, we don't have any framework code specifically for handles. That's because the details vary a lot between apps. For example, GraphSketcher's handles are a lot different from Graffle's, because the objects being manipulated are different.