I have added a LCD Screen to my Raspberry Pi and modified the headless client to give me status messages.
Here's a video of it in operation, http://youtu.be/oYb5f8sKivw, The plan is to build this into a controller and get flight mode status, etc on the screen - eventually I may switch to a full-colour screen and have virtual-horizon, etc. I'll write up some of the things I've done once I've tidied it up some more. it may be some time!
Very cool! I also thought about something like this, had a Graphical LCD in mind with the horizon and further telemetry data on it. Even got the LCD, but haven't found the time yet to tinker with it -- the usual problems
Is the source of your modified client available somewhere?
Also: AR.Drone 2.0 (RC-enabled thanks to self-soldered MiruMod) and Hubsan X4 H107
At the moment, the code is very messy, I have "lcd.py" in the "lib" directory, and am making the calls from lib/cflib/crazyflie/__init__.py
The problem is that at the moment, you have to be root in order to use the GPIO on the Pi, so until I've solved this I don't really want to show the code... Because I don't like it. The biggest problem with this is that you have to run the whole copter code as root - which is horrible.
I've taken a quick look at the quick2wire library - as you don't need root for that - however, I'm currently unable to get that to even turn on an LED on my Pi with Python2.7 - and of course, the crazyflie code doesn't work with python3 because of pyusb/pygame/etc.
Once I have a solution to this, I'll be sure to put the code up somewhere (probably my github channel).