In its latest update (1.7.0) Niantic has blocked the use of Pokémon GO on jailbroken devices, but luckily, we have among us a solution to continue enjoying the game.
The first thing to do is uninstall the game from your iPhone or iPad.
Subsequently, we add the following repository to Cydia:
http://xcon.crazy.net/Once added, we must access it and install "XCON" which is in the beta number 42.
Finally, just install new Pokémon GO to enjoy the game.
You see, this is a fairly simple method since the only function is to make XCON believe we have installed applications that have not jailbreak to our device.
Similarly, and although obviously we can not confirm 100%, it is assumed that it is a fairly safe method, since the power to run the application, Niantic should not know whether our device has not with the blessings of jailbreak .