This brilliant case from a a Chinese manufacturer (of-course) allows you to run Android on an iPhone, because isn’t that what you really want from life.
https://www.youtube.com/watch?time_continue=48&v=kE6TKBNKT6Q
MESUIT is the world’s first and only one smart hardware that runs Android OS on iPhones in the form of an app and supports one-key hot swapping.
Not only do you get an additional sim card, you will also get additional battery 1,700mAh battery for MESUIT for iPhone 6 or iPhone 6s while the MESUIT for iPhone 6 Plus and 6S Plus sports a slightly larger 2,500mAh battery. The smart case by Jijia runs on MESUIT OS 1.0 based, a custom Android OS.
The case costs about $150 USD for the iPhone 6/6s and about $165 USD for the iPhone 6/6s Plus.and is only on sale in China at the moment.