In the states, a company called OMG Electronics that unsuccessfully tried to raise money to build a smartwatch on crowd-funding site IndieGoGo, owns the "iWatch" trademark. The good news there is that the company will probably be open to selling the trademark for the right price. In the U.K., a company called Probendi has the right to the "iWatch"name. This company owns a monitoring smartphone app that "sends real-time audio, video and location data to the Critical Governance platform." The problem for Apple is that the trademark covers the entire EU.
Apple has already been through the Chinese trademark process when it ended up having to pay $60 million to Chinese company Proview for the right to use the iPad name in the country. In that case, Apple though it had secured the right to the iPad name throughout all of China, but had negotiated a deal with a division of Proview that had the right to the iPad name for Taiwan only. This time around, 9 companies have registered the "iWatch" name in China, but most of them are invalid. A trademark in force for the name "iWatching" might be enough to give Apple trouble.