Espruino, CLI, IDE, and Babel

Did I miss some docs somewhere or is a CLI like this not available?

You definitely missed something :) In fact literally just typing the command that you posted npm install espruino -g will give you a CLI: https://www.npmjs.com/package/espruino

There's also the ability to watch files so it'll integrate with your editor - just not with the exact syntax you posted :)

In terms of using it with Babel, I'd assume that there is already a framework for running Babel or other CLI tools when the source files change? If so, you could just add the Espruino CLI tool to the end of the list of tools to run - or could watch the output file of babel for upload with the CLI.

But yes, there's also thingsSDK for ESP8266, which wraps the transformations up as well.