There are a couple of threads on this topic, check out the search.
I think the camera on the N800/N810 is too low resolution to work well for this purpose. If you've had any experience with Sema or similar 2D barcodes, they can get pretty detailed. The N800 does what... maybe 640x480 at best (and pretty cruddy at that!)? I wouldn't hold my breathe on this being a viable solution.
