How can we patent roducts that are made for smartwatches and other 3rd party devices?

A patent is a negative right that provides you the right to exclude others from exploiting your invention. A patent does not give you the right to exploit your invention, for example, by manufacturing watches that incorporate your product, when the watches are themselves patent protected. However, obtaining patent protection for your product provides licensing opportunities with companies, such as Apple, which may be interested in using your technology in their watches.