Curse you and your inquisitive ways, Starsuperion! Oh very well, let's get back on topic and consider this interesting post that came out of Bristol University a few months ago.
So we start by manipulating "ultrasonic vortices" ... and include some sort of "sonic laser" that lets you project coherent beams of sonic energy. Perhaps this is how the Doctor is able to use his tool to start fires or cause sparks to fly off things he points it at, through some sort of SASER-to-electromagnetic conversion.
I used to think the Sonic Screwdriver was a daft notion. An icon for a futuristic multi-tool at best. Lately, I've been having second thoughts. I carry around several tools with me on a regular basis, including a multi-tool with customized UV and white LEDs added to the grips. It's an ugly thing but very useful, and different minerals and substances fluoresce in the UV light. In two or three thousand years, I think I'll probably add a few more useful gadgets to my multi-tool.
Anyway, I've also been thinking about the usefulness of a sonic screwdriver form factor for something like a remote control. Put a directional light on the thing, along with a series of unique sounds for specific functions. By itself, it's useless, but now throw in something like Microsoft's Kinect along with an audio monitor so a household computer can watch/listen for the device being used. Now, along with gesture recognition, the computer can watch what you point at, how you move the screwdriver, and listen to the sound to determine what action you want to perform. Naturally, all devices would have to be made controllable by the computer, but that's not hard these days. You could point your screwdriver at speakers to mute/raise volume/lower volume, point at a particular lamp to turn it on/off/dim, point at a monitor to turn it on, then point at a video source to select that input.
Given sufficiently advanced alien technology, a general-purpose multi-tool/remote might be capable of mind-boggling tricks.
