Yes..... I don't know the mechanism, as I'm not a game developer, but I was once playing one of the Angry Birds franchise, and locked the phone without leaving the game to answer my wife's beck and call, and when I came back a half an hour later I'd lost more than 50% of my battery level.
As for the Voice Butler, I haven't used that app, and I may not be following you correctly, but I can confirm that waitthereimaWP is correct, and apps that have timers, alarms or the like, do not use background agents the way many other apps do. When it comes to voice control, I do have an app with Voice Command functionality, and that does not require a background agent at all. It is surprisingly simple to create an app that uses voice commands, too. To give you an idea, tap/hold the start button, then press the question mark, and swipe from the right to see the list of apps you have installed that can use voice commands. You'll be surprised at how many there are, I suspect.