Application manager for Android
If you are running Android 2.1 or 2.2 you do not want to use app killers. It actually hinders performance and could cause more problems because Android has built in app killing functionality into the OS.

No app currently exists that can do all three of those. You can get an app that can do the first one, there are lots of those but I wouldn't recommend any of them. Or you can get an app that can do those last two...


Native Marketplace 
Uninstaller
AppBrain App Market
My Market
App Center - by AndroidPit