alerts-on-host.txt
My site is <stack> on <host>. I only find out it's broken when someone
tells me.

Set up the minimum:
- An external uptime check against a page that touches the database, not
  just the home page.
- Error reporting that emails me the real error and where it happened.
- An alert if my scheduled jobs stop running.
- One place I check each week to see everything is healthy.

Recommend free or cheap options that work with this stack, and what each
costs me to set up.

A check that loads your home page can pass while every other page fails. Point it at something that uses the database.