I have recently committed a version of gdb-ui.el to the Emacs CVS repository
(http://savannah.gnu.org/projects/emacs) uses variable objects to watch
expressions in the speedbar. This is achieved by using annotations level 3 and
the "interpreter mi" command (Many thanks to Jim Ingham et al, who contributed
this feature) and therefore requires GDB version 6 as well as the CVS version
of Emacs. It is similar, in some ways, to Insight. Indeed, the icons in the
toolbar are taken from there (with permission, of course).