This small application will allow you to avoid sleep mode.
Easy and fast: you can add a widget to enable/disable to 'keep screen on'.
Also, a notification is displayed when the app is On.
Example of usage: if you are cooking, then you don't want your mobile to switch off while reading the recipe!
Just activate KeepScreenOn, and enjoy cooking!
Important: you can still switch off your screen manually, even if the app is on :-)