[openbox] Displaying a window while key combo is being held

[fuumind]

Apologies for the threadjacking! Here's my question posted (hopefully)
in a correct manner:

Is there a tool in Openbox or X that I can use to display a window while
a combination of one or more keys on the keyboard are being held down
and then hide it again when the keys are released? Kind of like the
window switching dialog.

/fuumind