Could'nt the pressure part be skipped completely? I mean if the cameras are scanning the lines drawn as is, then it would record the output as it - so if you applied pressure the lines would be darker and the cameras would record dark lines.
I did see a post somewhere where a guy did this with a laser mouse as you are suggesting. It was not the prettiest of designs though
However, an interesting bit of information - the current optical mouse that we use has a small camera fitted in it which can be hacked and used as a low end scanner. That's where I got this idea from of using small cameras to scan the output. If a normal optical mouse can run for a couple of months at least using one AA battery, then if you use the same(ish?) technology and use three cameras instead then it might last you for 3 weeks or so.
These are all thoughts from figments of my imagination. I really do not have any knowledge in microcontrollers or computer hardware to actually figure out if this is a feasible / viable idea.
Here is another idea:http://www.youtube.com/watch?v=3zx5VFm6T8Mhttp://www.instructables.com/id/Mouse-Pen/http://www.tomsguide.com/us/Facebook-Like-Freedom-of-Speech-Aaron-Panner-Sheriff-Roberts,news-17042.html
And another idea, a bit limited in application though:https://www.shopstarter.com/s/gstick-pen-mouse/
Option 3: http://weblogg-ed.com/2007/the-wii-as-99-smartboard/
This is for large scale applications. Wondering if this could be scaled down?
By the way, in my reply, I was referring to something like this:http://forums.furtopia.org/tech-talk/turning-an-optical-mouse-into-an-optical-pen!-3/
All the media has been taken off that link, but that is the concept that I saw some place online. The guy sawed off a mouse, changed the mirror and fixed the optical mouse into a pen / plastic pipe.