There are a few options in App World for having a slide to unlock your homescreen option on your BlackBerry. To be honest, it is not something I have considered until I recently started using my BlackBerry Torch 9810 as my second device. Slide Lock is a simple customisable application which on the Torch works like a dream, although it will also work on non touch screen devices.
Features and settings:
As you will see in the above video Slide Lock will prevent your BlackBerry from making unwanted calls etc when in your pocket. The application will also let you set an autolock option on Native and Third Party apps which is pretty sweet.
"Slide Lock automatically locks your keyboard when the back-light goes off to prevent unwanted keypress activity. No more battery loss because you forgot to lock your phone and an accidental key press launched a GPS app in background. No more accidental calls because you forgot to lock your phone!"