A developer known as Hikari no Yume created earlier this year a tool called touchHLE that allows you to connect older iOS apps to Mac and Windows computers. Based on this project, another developer known as ciciplusplus created an iOS emulator for Android. In theory, it can be used to run iPhone apps on Android smartphones. However, it is too early to be happy about it.
The problem is that the touchHLE emulator, at least for now, works with some limitations, and it has the same drawbacks on Android as it does on PCs. For example, applications only run on chips with AArch64 architecture. Other than that, the emulator has only been tested on the Super Monkey Ball game so far.
As 9to5mac reports, emulating iOS on other devices is not an easy task, because this system is not only owned by Apple, but also designed to work on specific hardware. However, some developers are still able to successfully emulate older versions of iOS or iPhone OS. The point is that older versions of the operating system have much fewer security features and are "related" to much less complex hardware, which makes it easier to run them on other platforms.
Currently, users can't run the full version of iOS using touchHLE, but they can run some really old iPhone apps and games like Super Monkey Ball and Crash Bandicoot. Nitro Kart 3D.
You can download touchHLE for Android from the developer's GitHub page.