Collision detection (Drag, Drop and Slide)

I'm looking for someone to build a replica of the slide effect of email address tokens in iOS 5 Mail and to be applied to any object i.e. uibuttons. For an example see Mail in iOS 5. When you compose a new email and add a few email addresses to either the to or cc fields, emails with iOS 5 can now be dragged around. When an email is dragged and hovers over 2 other emails, those emails slide to make room for the "grabbed" email to then fit in place when dropped. Please provide rate and time estimate. Thanks