Serviio

I have the Web browser setup and a few family members have access. Is there a way of seeing who's actually using it and what they've watched?

Not really. The Serviio console will show real-time use, but nothing historical. When something is being streamed, there's a colored icon next to the device. Click that and it shows the title being played and a rough bar progress line. Although to be honest, I don't know if browser sessions appear here at all. It's something that I rarely use, and if I do use it I'm not at home, so have never paid attention.

The Serviio log might break it down to the user, but I've never looked at it so can't say for sure. If you want to look at the Serviio log, it's in the /log folder under the main Serviio install. For Windows, that's C:\Program Files\Serviio.