[CountSessine]

I wonder if this is going to make it to OSX at some point, given the commonality between OSX and FreeBSD?

[astrange]

OS X has provided such APIs for a while - you can create processes using posix_spawn rather than fork, and monitor them with kqueues.

That said, if you're writing an app you might be able to go higher level and use XPC services, which can be much less pain.