While I was at TechEd someone asked me how you detect a hardware keyboard on Pocket PC 2003 Second Edition devices. This could either be a clip-on keyboard or an integrated keyboard, depending on the device. Typically if the keyboard is attached you'll want to suppress displaying the on-screen SIP.
To detect the keyboard check the following registry key: HKCU\Software\Microsoft\Shell\HasKeyboard. This will be set to 1 if the keyboard is present.
[Author: Neil Enns]