I don't know, what do you mean by an "unrar binary"? If you mean an unrar JAR then yes, I could whip that into CBZViewer and rename it. Or you could post a CBRViewer!
Right now my weekend goals are to combine DJVU and CBZ into one viewer with a combined file format for saving the page number into.
My current thinking is to use the Sony Reader's <cache xmlns="http://www.kinoma.com/FskCache/1"> for the file. That way when I port things like my existing RTF reader and a Java PDB viewer I'll also have a place to stash the page break data.