I've also used launchd (OSX) for Serious Things That I Don't Want to Fail, and it was easy. One config file with a few details. Completely watertight abstraction, as far as I could tell.
Pretty much all of the new school init systems, loosely starting from 2004 onwards (Upstart, launchd, Solaris SMF, systemd) have glaring structural deficiencies in one way or another, from my observations.
It also has the odd benefit of already being cross-platform, so even if you move whole systems distributions (e.g., from Debian GNU/Linux to FreeBSD), you can still use that same knowledge there too.
Edit: Note that simple does not imply easy. Daemontools, for example, does not provide a means for doing dependency handling, so you'll actually have to engineer around that by writing a script to handle it. Same goes for bouncing things that go off the rails. Same goes for pretty much anything that does not fall strictly under the purview of starting a process and restarting it if it crashes.
Try this 150-line C program, it's good enough for that one simple task: https://github.com/urbit/babysit/blob/master/babysit.c