Build a pen that recognizes handwriting via an accelerator

I need a device that can fit inside the barrel of a large pen, that can detect what the user is writing with the use of an accelerator. Some guys in a university in Taiwan developped this type of device before. Here's their academic paper [login to view URL] Now, their's is 13cm long, I need it to fit in a common pen, or a custom built pen that looks like any other pen. Here's a sketch of the concept : [login to view URL]