I wish I had the money to buy the
Dell 2314T 23-Inch Touchscreen
so that I could start working on gesture based programs.
My concern with a program for all devices is that
it forces the desktop program's design into the space limitations of phones and tablets;
and desktop frameworks like Qt have powerful drag and drop widgets that make the interface much more customizable.
I would probably take the approach of
QtAV and make a desktop program and a QML app.
In short, I would make a desktop program and a separate phone/tablet program.
I think the result would be more appropriate software for each device.