The Staff Notes could be a good starting place. It integrates with users and posts, so you’d want to ignore the posts part and likely integrate with the user only.
You should also look at the Who’s Online plugin. That also deals with Users. However, the big difference is the Who’s Online is a global view, not specific to the user who is logged in, so you’d need to take that into account. But it also has several advantages for you, it is utilizing the message bus to send updates and that could be useful for you.