Semihosting does more than just emulate the standard I/O streams. It also emulates the filesystem. I've used this feature to get gcov-based coverage analysis

Semihosting does more than just emulate the standard I/O streams. It also emulates the filesystem. I've used this feature to get gcov-based coverage analysis out of an embedded target. You see, gcov normally expects to be able to write its statistics out to files which are named after the object files. Of course, those don't exist on a cross target. But with semihosting, you can fake it well enough to work. This also works for getting rich unit testing frameworks to work, too. Not only do they expect the standard streams to be available, you can also store a bunch of data-parameterized test cases for the unit under test in a file.