I used Google's AutoML Vision service (<a href="https://cloud.google.com/vision" rel="nofollow">https://cloud.google.com/vision</a>) to train the model off of pictures of masked and unmasked faces from coworkers and creative commons images from Flickr, and am running the model in-brower in a React app. It was pretty cool to see how easy it was to set up an object detection model without having to figure out how to set it up with Keras or something.
I recently built a similar system for HackOHI/O, my college's hackathon. Was a great challenge! We used a slightly different approach, as we didn't have the time or expertise to train our own models.