Is there anyway to lock the screen on an ipod touch?

okay so i want to see what is going on right not on the ipod, but, when i touch the screen it doesnt do anything, your answer can just give me a app or cydia app name and ill do the googling. The reason i want this is because some tasks need the ipod to be running (not sleeping). once i was in a hurry and i had to slip the ipod in my pocket,when i got back, it cancelled and deleted some of my stuff :[