Flextronics (NASDAQ:FLEX) could be assembling the iWatch, possibly right here in the USA. A couple reasons why this theory can be convincing:

1) Flextronics already has a relationship with Apple as they manufacture the Mac Pro. No leaks were released prior to announcement as they kept the project top secret. Flextronics is known to be able to keep top secret projects under wraps.

3) Flextronics already assembles some of the most successful wearables so far - Fitbit, Jawbone, and Nike

4) Flextronics shows heavy interest and investment in Wearable Technologies as seen in this whitepaper on their website and all the coverage from last year's Wearable Tech Conference