This is on current openSUSE FACTORY, so packages are pretty recent. 
X.Org X Server 1.9.3
Linux Kernel 2.6.38.x

In order to make the tablet switch of an Intel Classmate PC recognized, I added the following:

Section "InputClass"
        Identifier "evdev cmpc keys"
        MatchProduct "cmpc_tablet"
        MatchDevicePath "/dev/input/event*"
        Driver "evdev"
EndSection

Result:
[ 15160.987] (II) config/udev: Adding input device cmpc_tablet (/dev/input/event11)
[ 15160.987] (**) cmpc_tablet: Applying InputClass "evdev cmpc keys"
[ 15160.987] (**) cmpc_tablet: always reports core events
[ 15160.987] (**) cmpc_tablet: Device: "/dev/input/event11"
[ 15160.987] (WW) cmpc_tablet: Don't know how to use device
[ 15160.992] (II) UnloadModule: "evdev"
[ 15160.992] (EE) PreInit returned NULL for "cmpc_tablet"


evtest:
Input driver version is 1.0.1
Input device ID: bus 0x0 vendor 0x0 product 0x0 version 0x0
Input device name: "cmpc_tablet"
Supported events:
  Event type 0 (Sync)
  Event type 5 (?)
    Event code 1 (?)
Grab succeeded, ungrabbing.
Testing ... (interrupt to exit)
Event: time 1305897332.238400, type 5 (?), code 1 (?), value 1
Event: time 1305897333.174014, type 5 (?), code 1 (?), value 0


My idea was to get this button recognised as an input device and then be able to write a small applet which changes the xrandr settings once the machine is put into tablet mode.