Hi,
The Spy plugin is designed to work with Eclipse and Eclipse-based applications. It's mostly a proof of concept thing that I didn't take too far. Right now it only works with SWT toolkit.
In some near future I plan to open-source WireframeSketcher's Java model and the Spy plugin. This should make it possible for users to integrate WireframeSketcher in other workflows like yours. I think a Spy app for SWING is easy to implement since SWING is similar to SWT and it's all Java. I am not sure about QT but it's probably also doable if you use their Java interface.
Best regards,
03 Jan 2010