What do I need in terms of hardware and software in order to start recording my own classes in Khan Academy's format?

Hi, everyone.

My name is André. I'm a math teacher from Brazil, and big fan of the work you do here at Khan Academy. I would like to record some classes. What do I need in terms of hardware and software in order to do that like you guys do? Here in Brazil I see lots of online classes with teachers in front of the camera, using a blackboard, like it has always been done. I'd like to try it in Khan's way. No teacher appearing, just audio, images and my writes. Could you give any help on this? Thanks a lot!