Earlier quoted context omitted.
Firebase engineer here. For things like chron jobs / emails / any logging you want to do, you can run a node server that uses the javascript SDK. That lets you do things like, "any time a user writes to this location, send an email with the contents of the data". You can also observe arbitrary data changes and log any info that is relevant to you. As for passwords, we have a few details here at the bottom of the page…
A node server that I run on my server accesses Firebase through the SDK, right?
You can also use the REST API (https://www.firebase.com/docs/rest-api-quickstart.html) to interact with Firebase from any platform.