"Security Enhancements for Android (SE for Android) is a project to identify and address critical gaps in the security of Android. Initially, the project is enabling the use of SELinux in Android in order to limit the damage that can be done by flawed or malicious apps and in order to enforce separation guarantees between apps. However, the scope of the project is not limited to SELinux."
In fact its part of the latest Android distributions (Android 4.3+) but its not generally enabled by default yet. Eventually we should be able to lock down the device to prevent all kinds of malware, but unfortunately it doesn't block users from being stupid and installing apps from the more seedy places. Chances are if you install a hacked app you'll just grant it all kinds of permissions that you shouldn't. It can't fix 'stupid'.