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