The monitor works well for what it does, but it's very much so cobbled together. HTML is hand generated. Static state is used liberally which makes testing near impossible. View and controller logic are tightly intertwined which also adds to the testability problem.
I've been working on porting the functionality from the existing monitor to a proper rest service using dropwizard. It's not completely functional yet, but it has a number of improvements of the existing monitor code.
I thought I would post what I have already and let people give some feedback if they're interested. Help is always welcome. https://github.com/joshelser/accumulo/tree/dropwizard.