I have found it - the ultimate computing chair/pillow contraption. It's called the Sumo Omni and it most closely resembles a big-arse pillow and glorified bean bag. I first heard about it from Derek Punsalan a year ago and I've had my eye on it ever since. Unlike most reviews of Sumo products you'll see online, I actually bought the 129 Sumo Omni myself.
In the 24 hours I have owned the Omni, it has already changed my computing style. Rather than being bent over on a chair while working on my desk, I have experimented with several computer-friendly positions.
As with any bean bag product, the Omni conforms to your needs and can be shaped however you want. Unlike other cheaper bags, the Omni is constructed of sturdy nylon, which isn't quite as soft as anything like cotton but it is rip proof and will last. It also has the added benefit of sliding quite nicely on wood floors - always a plus.
The Omni can also function as a makeshift bed for unexpected visitors, although they might be a bit sore in the morning. I accidentally dozed off while writing this yesterday and was quite pleased with its large size. The only real problem with the Omni, which is shared with most bean bag products, is that its hard to get up from one, especially after you've sunk in and made your own space. Other than that, I love this thing.
If you have an extra football field or two of space in your dwelling, definitely take a look at the Omni. Do you have space for one at your place?