Thanks for your interest in our products. For smartwatches we recommend our Intel® Quark Processors. Of special interest for your application could be the Intel® Curie Module, this is a brief description from the fact sheet:
To speed the development of wearable products based on the Intel Curie module, Intel is providing a complete software solution that includes a small and efficient real-time operating system (RTOS) together with reference wearable applications called Intel® IQ Software Kits. The kits include the embedded software that runs on the module together with companion smartphone applications and associated cloud capabilities.
Here you can check the specifications of the products mentioned:
If you want more specific details about this platform you need to apply for a Privilege Account at the design center: Register for a Privileged Intel Account , that would allow you to receive Intel Confidential Material for the platform, as well as more support during the development of your design.
I hope this information is useful for you.