Thanks for the ideas. One thing I have wrestled with in the past is how to prevent exposing the third party site email credentials (credentials the page would utilize for accessing Sendgrid, etc.) if the emailing code were hosted in the local and observable JavaScript. With the current server solution, at a minimum the browser and CORS enforcement take care of attempted cross domain access ... which is probably just slightly better than nothing at all.
The motion detection takes place in the browser with JavaScript which analyzes and quantifies RGB value differences. HTML5 takes care of the camera. An email server is still required - HTML5 doesn't cover that of course. This works with up-to-date Firefox, Chrome, Edge, and Opera browsers on Windows, Mac, and Android (the OS specific browsers running as applicable on various platforms). I am currently aware of just Safari and iOS on iPhone/iPad not working - the camera view shows all black and I have not yet attempted to solve.