You can shrink the lens and CCD down that far[0], but adding in a power source and data storage is likely to increase the size. Batteries are not tracking other improvements in technology. Additionally with a lens that small you're almost certainly going to want some form of image processing. You can move the problems of storage and process if you want to radiate or have a wire, but those introduce other concerns. Shrinking the entire package down to a grain of rice seems overly optimistic.

[0] http://lanmdagigi.en.ec21.com/offer_detail/Sell_The_smallest...