[NTLK] Hi there - Big question

[Tim Kaluza]

Hello!

I'm searching a kind of device, that has a similar function for writing and sketching and mathematical functions useable. 

I mean, I'm right now studying and wold love to use a electronic device instead of a pen and a paper, (because I like having it in a digital form) 

I tried the IRIS:
http://www.irislink.com/c2-1626-189/IRISnotes-------The-Digital-Pen-that-types-what-you-write-.aspx

Is there anything else? 
Could also be something like the iPad - but I need a writing device - because it's got the most speed when you have forms and mathematical things to write. 

Any idea?

Your's sincerely 
Tim K.