This post :
http://forum.stmlabs.com/showthread.php?tid=5517
shows that you cannot normally get to the CLI from within Raspbmc, however, this particular post
http://forum.stmlabs.com/showthread.php?tid=5517&pid=45120#pid45120
seems to show that it can be done using python.
sudo apt-get install python-dev <--Installs the Python development?
sudo apt-get install python-pip <--Python package installer
then create a file, that contains python script: Code:
import subprocess
subprocess.call("sudo /etc/init.d/transmission-daemon start", shell=True)
and last, assign this script to a button on remote:
RunScript(/home/pi/.xbmc/userdata/pyscript/your_script.py)
I suppose that this gets you to the CLI where you can do your keyboard magic