The Doctor's "omnitool" started out as something rather simpler - a sonic lockpick. Now the screwdriver has been used to amplify sound waves, as a flashlight, to disarm weapons and electronics, conduct medical scans, remote control the TARDIS, perform molecular engineering...all kinds of things. And, yes, as a screwdriver.
In other words, it's a plot device. A widget. It can't possibly work or exist in reality.
Researchers at the University of Bristol (not that far from Cardiff) and Dundee have now created what they call a sonic tractor beam. So far, they can use sound waves to levitate and manipulate polystyrene balls up to 5 mm across. They're hoping to shrink it down to a size that would be useful in medical operations.
But working from that to a device that can pick locks and unscrew screws? It suddenly doesn't seem all that unreasonable at all. (Presumably, the flashlight function is an add-on).
So, while we won't be wielding sonic screwdrivers any time soon - they may not be quite the amazingly advanced technology from an alien race after all.