If you're already setting up a separate server, why not use MOM?

I've looked into that and cannot find a rule to monitor failed jobs. If I have to build this rule myself, then why not go for a tailormade solution anyway?

Personally, this seems like a lot of heavy lifting and manual labor, and the effort involved seems to outweigh the costs of commercial tools already available.

This is correct, however, have you even looked into the extra load some of these tools add to a server? Dunno about Sentry's Eventmanager, but others where a firm no-no after a day or so of testing. Idera JM was 1 of those.

For job monitoring, I just get each server to send an email (per job) when a job fails.

Yes, nice 1, we have more then a 1000 jobs running all over the place, and alas, not only the DBA can go there and add/delete jobs. I prefer a central monitoring system.

However, I miss the job to run this setup. I can figure it out, but do I miss something here? It's not part of the download?