[openbox] how to kill an application by pointing at it?

[Jim Rees]

Back when I used twm, there were two menu items that could be used to kill
an X application. You would choose the menu item, the mouse pointer would
change to a death-head, you would click on a window, and that window would
go away. One item worked by asking the application to please close itself,
the same way the close button works (it was really only useful for windows
that had no title bar). The other worked by forcibly closing that window's
connection to the X server.

I know there are a few ways to close windows from Openbox, wmctrl for
example, but I don't know of any that let me select the window using the
mouse pointer. Is there a way to do this, either via Openbox directly or via
some X application?