>I am wondering if IOS could add a new feature to detect bad apps.
I think Apple can add such as a step into their build process (IIRC, with the new XCode 7 there's the option to submit a kind of bytecode to be built on Apple's servers depending on the target architecture etc).
Another thing they could do is enable some kind of "Little Snitch"-like network connection that a user can enable for apps. This way the user can be informed for any "mysterious" external connections going on.
For example IOS could give an operation history summary for each App. The list could be something like this:
APP1:
Photo ---- read ? times write ? times
Contact ---- ...
sms ---- ...
device ID ---- ...
APP2:
Photo ---- read ? times write ? times
Contact ---- ...
sms ---- ...
device ID ---- ...
customer can turn on/off this feature.
I believe if IOS have this feature, it will be much easier for IOS user to find out the bad APP.