The security model that Windows Phone uses doesn't allow apps to be aware of other apps, and doesn't allow them to explore other apps' data, use, etc. So what you're looking for isn't possible (unless it were to be built into the OS, that is - would be a nice feature to add, MS).
That said, there is a roundabout way to get an idea of where the battery usage is, provided you have Data Sense, and since you're posting in the 928 forum I'll assume that's the phone you have, so you do. If you look at the apps that are using the most data, there's probably a good idea of who's using the most battery. Of course this isn't always going to be the case, especially with games, which may be using high power without using much internet... But it can help to narrow things down some.
With only 82 posts here and over 1250 global posts, I'm going to assume that this is your first Windows Phone (apologies if not), so welcome to Windows Phone. Here's another thread I started that goes into detail on the background tasks and such. While rare, it is possible for background tasks to use a lot of battery. A background task is allowed to run for 25 seconds, and will run approximately every half hour (30 +/- 10 min). Given that, it is possible for a single background agent to be processing for up to 30 minutes in a 24 hour period. Most won't run near that long, probably many for not even a second, but if you've got apps that are running long background agents (and unfortunately there is no way to know how long they are running), and you have several of them (I'm running 12 background agents now, but have run up to 15), you can see how this could quickly add up.
Here's that link I mentioned - good knowledge if you're interested in it.
http://forums.windowscentral.com/wi...naging-background-apps-why-you-dont-need.html