So I know about the Mercurial activity extension, however the data it seems to plot is number of commits. I don't think that is a good metric. If in an hour you make 20 commits or 1 commit, I don't think one can deduce much from that. I think it's far safer to say every time there is a commit we assume/input some previous time of work was done. 1-2 or maybe 5 hours (depending on the person). Then you plot that in a block style calendar widget (like github's contribution widget) either by week or by month...
Does anything like what I describe exist?