Thumbpad is a tool to translate multiple numeric key presses into alphanumeric input like known from entering text (e.g. a SMS) on a cellphone keyboard. It is a Xembed dock applet and compatible with the Gnome panel "Notification Area", matchbox-panel and fbpanel.
You can build and install Thumpad in this way:
tar xzf thumbpad-0.x.tar.gz cd thumbpad-0.x ./configure makemake install
If you have matchbox-input-manager installed you can activate and deactivate Thumbpad with it.
Additional information like project news, and CVS access and downloads can be found here.