I gave a quick shot to CellWriter. It's packaged in Debian and
probably in Ubuntu too. The one feature I liked is that it's able to
send the written characters directly to the currently focused window,
even though this window may belong to another program. It does so by
faking X key press events. Looking at the source code of CellWriter,
it appears that it uses Xlib directly. Currently, scim-tegaki can
achieve the same functionality thanks to scim but tegaki-recognize
can't: it just copies the characters to the clipboard.
There appears to be no straightforward way to do the same in GTK
(maybe in Qt?), but I found several links with workarounds:
http://wwwx.cs.unc.edu/~gb/wp/blog/2007/11/16/sending-key-events-to-pygame-programs/comment-page-1/
(see also http://live.gnome.org/GAP/PythonATSPI)
http://www.daa.com.au/pipermail/pygtk/2005-December/011535.html (see
also http://developer.gnome.org/doc/GGAD/sec-gdkevent.html)
However this code is highly platform-dependent...
Mathieu