It depends on how you do it. I created a View Controller that has an SPView set as its view property. When the user selects a level, I load it as a model view controller. When the game is over I dismiss it a load another model view controller that shows the game over screen.
This way I'm not running any Sparrow process until the game starts being played and I stop all the process, and remove the SPView from the memory when the game is done.
I'll try to get my view controller up on the Wiki tonight.
BTW: I have not used the scaffold project since v0.7, at that time it was set up to start Sparrow right away. You have to change the set-up so it does not do that.
UPDATE: I put my GamePlayViewController on the Wiki. http://wiki.sparrow-framework.org/extensions/gameplayviewcontroller