Today, Cydia creator Jay Freeman (Saurik) released an update to his tool Cydia Impactor, which allows the signing and installing of .ipa files to iOS devices.
With it comes a new tool called Cydia Extender, which allows installing and re-signing of .ipa files on-device. However, don't get too excited by this news; it is not the solution to the 7-day signing problem that many have been waiting for.