You can detect when your are scrolling with delegate methods of your UIScrollViewDelegate like scrollViewDidEndDragging:willDecelerate:
and scrollViewDidEndDecelerating:
Add your label in your xib in the place you want and set alpha property to 1.0 when detect you are scrolling and alpha property to 0.0 when stop it.
You should have a XIB with a structure like this:
ViewController
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View
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UIScrollview or UITableView
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UILabel
Your label must be subview of your view and no of your scrollview and to be always in front of your uiscrollview