Though little is known about the patent filing, it seems Apple may not have gone to the same lengths of secrecy it did when filing iPad patents, where it used shell companies to conceal its identity and thus circumvent the problem of giving away details of future products.
A quick search of the US trademark database shows numerous filings for an "iWatch" trademark, some alive and some dead, and while some of them are for digital monitoring services, others pertain to sensor-laden wristwatches. None of them are evidently owned by Apple. The company is nevertheless said to be intensely interested in smartwatch technology, having built up a large team earlier this year. Tim Cook also recently noted that in terms of wearable tech, the wrist is "interesting."