For anyone who is interested I have established a point of sale client application to which anyone using the 770 can open a touchscreen display and operate the POS app on the remote computer. You need only have openSSH installed and X forwarding enabled.

Let's first see if you can display our instance of "X Eyes" - xeyes - on your 770. If openSSH is installed, open the X terminal and type The POS computer will ask for a logon password: demo when the password is entered the 770 will download some fonts and textures, then get xeyes.

If that works, close the terminal to close the xeyes display. Open it again and type
The POS computer will ask for a logon password: demo
when the password is entered the 770 will download some fonts and textures, then get a START screen.

Any user ID from 1 to 5 is OK, then select FastStart and you should see the pizza menu. Any button that has '2X' on it is a double-tap or double-touch button.

I'll await for feedback to finetune the demo.

There is an entry in the Wiki that covers the setup for X terminal and OpenSSH.

The demo works for anyone running a desktop with an X terminal and SSH, too, as long as SSH is configured to allow X forwarding.