Anyone know of a smart and live document system?

Hey IH!

I've got an idea, but I feel like it must already exist and I just haven't come across it.

I'm looking for something similar to Google Docs, but as powerful as Excel, with the ability to bring in plugins and 3rd party widgets like a web page:

1. Insert a variable (or a "cell", in Excel speak) anywhere in the document.
2. Create and use as many variables as you want, of course. Reference them anywhere.
3. Insert Excel-like spreadsheets within the document (similar to how Numbers does it).
4. Bring in widgets like calendars, to-do lists, charts, etc., that are fed by live data -- i.e. dynamic, not static.

Quip seemed to be headed that way, but has since become Salesforce Anywhere.

Anyone using something good? Or actively developing a solution?