I'm using the TclKit distribution at:
Unfortunately, it isn't an easy problem to solve. The n770 might run
Linux but the supplied windowing environment (Hildon)is quite different
to your typical X11 window manager.
Meredydd Luff did a bunch of work on interfacing Tcl/Tk with various
Hildon features - those mods are in the tclkit you've been using. As
you've noticed, integrating with the Hildon virtual keyboard wasn't one
of the mods, and will probably require Tcl bindings to D-Bus and/or libOsso.
Alternatively, you could take the approach that Steve Redler did and use
one of the pure-Tk virtual keyboards from the Wiki.
Steve