The general idea is that you build a JMeter script that gets run from ant. So after every automated build/deploy the ant task generates an XML file showing the performance for that build.
The JChav ant task then operates on the stored XML files to produce a set of charts. Each chart shows the performance of a given page for each build that has run. Each chart shows you how the performance of the page has changed over time. That way you can show everyone how much better your code is improving (or not) over time.
Pictures are worth a thousand words, a live demo is available here showing some statistics on accessing digg.