Paul Reinhemier has written up post sharing his creation of the code to get XHGui working with MongoDB.

Mark Story & I are pleased as punch to introduce XHGui on MongoDB. Our goal was to get as close to the original feature set of the tool I worked on a few years ago (which leveraged the starting point provided by Facebook) and then to release what we had. What we've got now works; there's still a good distance to go, but we think it's far enough that we can ask for help form the community at large.

The tool collects XHProf data and stores it into a MongoDB database and allows you to view recent activity. There's a few warnings that he includes with the post, so be sure to read those through if you plan on using the tool.