Except for the usual prohibitions against narcotics, explosives, plant and animal materials, firearms, and ammunition, you can bring anything into China that you plan to take away with you. GPS equipment, cameras, video recorders, laptops, and the like should pose no problems. However, China is very sensitive about printed matter deemed seditious, such as religious, pornographic, and political items, especially articles, books, and pictures on Tibet. All the same, small amounts of English-language reading matter aren't generally a problem. Customs officials are for the most part easygoing, and visitors are rarely searched. It's not necessary to fill in customs declaration forms, but if you carry in a large amount of cash, say several thousand dollars, you should declare it upon arrival.
On leaving, you're not allowed to take out any antiquities dating to before 1795. Antiques from between 1795 and 1949 must have an official red seal attached.
U.S. Customs and Border Protection (877/227–5511. www.cbp.gov.)