Thank you for the responses. I'm a math major and I use paper all the time for sketching out proofs and formulas, both which would need a good resolution to do electronically, and the standard A4 paper size. I do like the idea that I could be reading a math book and I get an idea that makes grabbing a piece of paper a hassle so I would just write in the book itself without physically damaging the pages.
So it sounds like the iRex is the closest thing out there next to a tablet PC that can do this(I have a Rocketebook 1150, but since its a touchscreen the resolution is severely limited as well as the occasional error while writing), but the screen size might be too small to work vigorusly on long formulas. (No I don't plan on getting a chalkboard, its too messy).