iAppConverter is a tool that allows you to convert apps to run on different Apple platforms than they were originally intended for.
Looking for a tool that lets you convert iOS apps to Mac Catalyst apps? iAppConverter doesn't support this yet. In the meantime, check out my fork of @stroughtonsmith's marzipanify!
This is the iPhone calculator app running on an iPad. It has oversized buttons, but otherwise works well. With a couple tweaks, Apple could ship this on iPad.
This is the same app running on the iOS, tvOS, and watchOS simulators, all converted from an unmodified iOS Simulator binary.