Help Me Lose My Bag

I don't want to carry a backpack around anymore. Ideally, I'd go to work, or out in general, with nothing more than what I could fit in my pockets. Further, I'd not carry some ridiculous amount of stuff in those pockets. I'm looking for novel ideas for how to reduce the amount of gross stuff I carry on my person on a daily basis.

What do I carry now? I carry a cell phone, a pen or two, keys and a wallet in my pockets. In my bag, I carry a book or two, a notebook (paper, I stopped carrying my computer a while ago), and whichever papers I'm currently reading. In addition, I usually carry some Tylenol/Advil. So I'm already traveling pretty light. But I still think I could do without the bag if I could replace the paper notebook and other books somehow.

Currently, I'm inclined to believe that technology is the answer, at least in part. It seems that many people love to get high and mighty about low-tech when answering questions like this ("I've got some technology for you, it's called a 'pen'"). I have no problem with low tech, but low tech won't make my textbook fit in my pocket. Similarly, the reason I carry a notebook is because it holds all my paper/papers together in one unit. So a PDA is probably a good step toward eliminating books and some paper: it can store and display both ebooks and pdfs, as well as a calendar and address book (which I currently do not carry with me; if only I could sync my phone with Google Calendar....). The PDA would even be good for jotting down quick notes.

Where PDAs fail is in any longer form documents, or the real killer, when I need to write down math (which is much more common than any other type of prose I write these days). For that, I don't see how I can avoid pen and paper. However, services and software like scanR are making me think that all I need to do is take pictures of math done on a piece of paper or whiteboard, and then I can have that transformed into clean, digital notes that I can look at later. My phone's camera isn't sufficient for this, but I might consider some other phone or a whole separate digicam for this purpose, if it really worked.

But those are just my ideas; I'd love some help coming up with some novel solutions to not carrying around a bag. Maybe there's a different way to factor the functionality I need? Maybe I should switch to some sort of bandoleer? I'm open to suggestions; how do you keep from lugging around excessive extra storage? What PDA would you recommend for someone who wants to obviate his notebook? Are there any devices out there that are good for writing down math? I look forward to your comments.