[UTSAFTW]

I just use the Titan's built-in Device Lock on the today screen. It has worked fairly well for me so far.

I'm not sure about other carriers, but on my Sprint branded phone I have it. If you don't see it, you can check to see if you have it going to:
Start->Settings->Today. Then select the "Items" tab on the bottom and select the checkbox for "Device Lock".