It's interesting, but there is surprisingly little (next to no) details. Are you using map/reduce or Aggregation framework? Is the data out to be consumed by say Ruby client or are you just displaying results on the web? Looks like a pure landing page just to test to see if there is interest. If that's your intention, I don't like baiting HNers instead of just asking. If not, I recommend to put some examples, use cases and more information before posting here.

How does it work? If I have a collection/table with 100,000 rows and want to create a histogram by month does it pull the 100,000 rows over the wire to your servers and does the aggregation there?

  select month, sum(x) from T group by month;