Cydia Impactor is a new tool created by Cydia founder Saurik, it is a very special tool for jailbreakers that has the ability to remove or clean all data (the jailbreak related) on your iOS device, without needing to upgrade or restore your device.
Its principle is actually same with iLEX RAT and Semi-Restore, all of which allow you to unjailbreak your iOS device to stock without upgrading. Different is the Cydia Impactor works only need a working Internet connection, no computer or wires, it uses official OTA firmware archives to repair the damaged iOS files to restore your device back to its pure state.
Cydia Impactor is actually very useful in some cases, such as you can use Cydia Impacter to remove jailbreak and clean all data of iPhone before you selling it, to increase resale value. The advantage of this is that you can avoid a firmware update to clean your iPhone, while retaining the jailbreak.
Cydia Impactor 0.9.15 is available at Cydia Store for free, it is currently in beta for iOS 8.3 and iOS 8.4 only.
HOW TO ‘SEMI RESTORE’ JAILBROKEN IPHONE USING CYDIA IMPACTOR
Step 1: Backup your iOS device using iCloud or iTunes
Step 2: Make sure that you device is plugged in, and has at least 20% battery life
Step 3: Install Cydia Impactor from Cydia
Step 4: Run Cydia Impactor by tapping delete all data and unjailbreak device, then tap the Delete All button to confirm. Once the process begins, be sure not to touch your device until you see the iOS setup welcome screen
Step 5: Once completed and at the welcome screen, go back through the initial iOS setup process and activation