http://www.sencha.com/forum/showthread.php?115907
http://blog.extjs.eu/know-how/extension-or-plugin/
Here's a simple clock extension I created using Raphael extending BoxComponent. I'll be demoing this at SenchaCon 2010 tomorrow, hope to see you there

To try it out, drop it into the Ext JS 3.3 examples folder.
Live Demo: http://ext-scheduler.com/playpen/senchacon/index4.html
/Mats