Gimps Question: Resizing a selection or layer

[Joel Hammer]

Is there a simple way to resize a selection or layer in Gimp?

Ideally you would just outline the selection, and then change the size
by grabbing and moving anchors on the selection with the mouse.

Second best would be a similar operation carried out on an entire layer.

The only method I see now is to use the scale layer option in the layers box
(right click). This is very unsatisfactory.

What I want to do is insert a "virtual" ruler into medical photographs, but
I need to resize the virtual ruler to match a real, although tacky, ruler
in the original image.

Thanks,

Joel