Chances are high that if you own iPhone or iPad, you would be familiar with Cydia. It is sort of App Store for jailbroken iDevices where you will find lot of tweaks to customize your iDevice according to your liking. Emulators like iOSEmus are not allowed in App Store, so they found their way to Cydia.
iOS 11 was released last month while iOS 10.2.1 has been available for quite few months now. Thanks to a new jailbreak developer named Abraham Masri, a new jailbreak and nonce setter tool called Saigon is released. This tool allow iPhone, iPad and iPod Touch users to successfully jailbreak their iDevices running on iOS 10.2.1 or iOS 11 without any issue.