I downloaded the PleaseSleep application, which seems to work just fine!
But its really really ugly and there is no setting to hide it completely, remove the menu bar icon or the floating window, you must have atleast one, and i would like it to run completely in the background. I really dont need to change any preferences at any time.

So how's this done?
Using it on my netbook too, therefore i need the space in the menu bar, cause of the low resolution.