Try Pocketshield.
http://www.pocketshield.net/
You can DL the CAB and use the trial version. It has a built in call lock screen, and TONs of other options. My fav is the light sensor unlock feature! A text comes in while the phone is in the case, and the screen won't unlock until the phone comes out of the case and gets enough light to activate it. There's several skins for it as well.