Force Your iPhone Apps to Be Taller Using FullForce for iPhone
Ryan Petrich has released a new tweak that forces apps without support for the iPhone 5 to be taller.
Force legacy applications to show in fullscreen mode on the new taller iOS devices
Notably, users can choose which apps use FullForce and which do not via the Settings app. You can purchase FullForce from the Cydia Store for $0.99.
(Please note that this may not work perfectly with all apps.)