Facebook Inc (FB.O), United Continental Holdings Inc (UAL.N), BMW AG (BMWG.DE) and others have spent weeks at Apple’s headquarters, working with the smartwatch to test and fine-tune apps that will debut alongside the device, Bloomberg reported, citing people familiar with the process. The watch, which will let consumers check their email, pay for goods at retail stores and monitor personal health information, will be Apple’s first major product launch since the iPad in 2010.