If you are already looking for a Christmas present, you might find a good one for your brother in U.S. Patent No. 6,966,840. The patent is titled “Amusement device that senses odorous gases in a bathroom.”
With all this question of patentable subject matter — perhaps this would have been a candidate for rejection. . . . Proposed revision to Diamond v. Diehr: “anything under the sun made by man [excluding bathroom related novelty devices].”