Nokia N95 and Nokia N82 are the mobile phones which have accelerometers within themselves, and so the innovative apps are available for only these mobile phones whose shake features can make functionality available in the mobile phones.
Shakelock app for Nokia N82 and N95 phones is the one which can help you use the accelerometer feature to lock and unlock the keypad with just a shake of the device. When you install the app and enable it. You just have to shake the mobile device down and up, and the keypad gets locked.
And when you shake sidewards, the keypad gets unlocked.
So you don’t need to use the keys to lock/unlock when you have Shakelock app for that purpose. Its an innovative app developed for accelerometer enabled Nokia mobile phones, and this is in beta stage so you won’t expect more features until its official release.
You can download Shakelock from here or here.