[Q] any apps to replace power button for screen lock-unlock??

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I feel ,there is some issue with power button on my tab7.7 , because when i press power button to on or off screen..Sometimes screen shows like rainbow color scattering ...or yellowish bright dots mark, like sand all over on display with black/blank background .
i have to press power button again to get it back normal..So seems there is a issue with power button or power supply to display.. so to make minimal use of power button.. i am looking for any apps... which replaces power button with volume button for screen on-off(lock-unlock) only..
please help ..i have no much idea about..
thanks in advance.

Lock & Screen Off Widget by fsinib. But there are many others.

im using Smart Screen On Pro version and it works awesome

thank you both guys for the suggestions
Lock & Screen Off Widget by fsinib ,is not what , i am looking for, but Smart Screen On LITE..is what exactly.. i am looking for.. i tried it ..but not satisfied with its response, so i kept looking for another one .. and found TapTap app. .. seems it responses better than Smart Screen On .. but even not 100% accurate, but surely..it reduces almost 90% use of power button..

TapTap doesn't support ICS. However I've found Smart Screen works flawlessly on ICS. (I have a custom ICS rom called QuickSilver)