Here are my notes as I find things relevant to using this touch screen:
$ lsusb Bus 001 Device 002: ID 04e7:0020 Elo TouchSystems Touchscreen Interface (2700)
Installed Jaunty Feb 18 09 - out of the box I get X's display, and the mouse 1/2 works: touch center of screen, mouse cursor jumps to center. drag finger up, mouse follows (good.) drag finger to the left, mouse goes to the right. that's a problem.
Manufacture has linux support: Version 3.1 April 14, 2008 http://www.elotouch.com/files/install/elo_linux_serial_driver_v3.1_installation_instructions.txt http://www.elotouch.com/Support/TechnicalSupport/Drivers/Linux/ (have not tired it yet, hoping to only use ubuntu packages.)
/usr/bin/calibrate_touchscreen /usr/bin/ev_calibrate /usr/lib/xf86-input-evtouch/calibrate.sh /usr/lib/xf86-input-evtouch/ev_calibrate
https://help.ubuntu.com/community/EloTouchScreen "Note: Version 1.1.0-3 has a bug that is triggered when axis minimum and maximum values are inverted. Until the package is updated a patched version (1.1.0-3ubuntu1) is available from my PPA. "
http://www.embedded.com/story/OEG20020529S0046 "Steps in the calibration process" - looks like a description of how to write a calibration program.