An upcoming tweak available only to those who have jailbroken iDevices will allow for turn-by-turn voice navigation directly through the native iOS Maps app. iOS users have had to turn to (mostly quite expensive) third-party apps if they wanted this feature, while iOS competitors such as Android have had this feature built-in for quite a while now.
Unfortunately, as Apple is very strict regarding what developers are allowed to make use of on an iDevice, and of course will definitely not allow modifications to its own software, something like this would only have a chance on a jailbroken iDevice. Tweaks such as this only give more of a reason to jailbreak, until Apple (should it ever) chooses to further open up development on its products and allow for modifications like this.
This tweak should be coming very soon to the Cydia store, although there is no set price on it just yet. You can watch a preview video of the new tweak below, and stay tuned for the upcoming release.
If you’re looking to jailbreak your iDevice (and you’re on iOS 4.2.1 or below), you should also take a look at the newest untethered jailbreak known as Greenpois0n.