Does anyone know of more such 'hidden gems'? I really want a self-hosted website uptime (http status code) checker but I can't find one.

Why? That's an hour's work or less to write.

Nagios: http://www.nagios.org/

Was not familiar with Amon before-hand. What makes it better than munin, or the like?

What is "amaon"?

I think he means https://amon.cx/.

Ahhh, thank you!

I tried googling, but kept getting asked "Did you mean amazon?"