Wacom has just introduced a rather interesting product called Inkling. Kudos for coming up a product that mimics the tactile feeling of drawing.
It consist of a receiver that you clip to your drawing surface such as a notebook, and a Wacom ballpoint pen. While you're drawing, the receiver will record your lines — your drawing — and allow you to open them digitally after you transfer to your computer via USB.
The retail price is set to be US$199. I hope they don't charge ridiculous prices for their ink cartridge.
Derwent has two products that go with their Inktense brand. One's the pencils and the other's the blocks. As with Inktense, the colours are really vibrant.
Here's a video on how to use them posted by Derwent.
Derwent Inktense Blocks are available on Amazon (US | UK | DE)