Here's a piece of news that kind of flew under the radar during saurik's update of Cydia Installer earlier today—he's apparently working on providing a version of Cydia Impactor for iOS 9 firmware, too.
Cydia Impactor was the groundbreaking jailbreak release that allowed iOS 8 jailbreakers to perform an erase and restore on their devices without necessitating a software update. It basically allowed you to use iOS' Erase all Content & Settings feature in such a way that it worked with jailbroken devices.
That tool was groundbreaking, because jailbroken devices, up until that point, were never capable of using this built in iOS feature. Cydia Impactor adds significant peace of mind to jailbreakers, because if something goes wrong with a jailbroken device, it's possible to restore on the same firmware, and re-jailbreak.
In the past, jailbroken iPhones that needed to be restored were forced to update to the latest firmware, which, more times than not, would render the device un-jailbreakable. As you might have noticed, Cydia Impactor doesn't currently work for iOS 9, but saurik is working hard in an effort to fix that.