Matt Curry has this recent post looking at the CakePHP Status plugin he's developed and how to add in a custom Ajax-powered panel.

Last time we made a simple panel that showed the last 10 users that signed up for you web app. [...] This time we'll do a panel that shows the number of sign ups based on a time frame. We'll add a drop down that let's you select day, week, month or year and it'll show a breakdown of new users for that period. The updates will use ajax.

He includes the code to create the element, set up the javascript to interface with the backend and the PHP to create the controller for it to interface with. His example grabs the most recent signups from his Users information.