Good questions, guys - the GMAT letter of the law is a little vague, but I'd pay attention to the "including, but not limited to..." line when planning my test strategy:
No testing aids are permitted during the test session or during breaks. Aids include but are not limited to beepers, pagers, pens, calculators, watch calculators, books, pamphlets, notes, blank sheets of paper, rulers, stereos or radios, telephones or cellular (mobile) phones, stopwatches, watch alarms (including those with flashing lights or alarm sounds), dictionaries, translators, thesauri, personal data assistants (PDAs), and any other electronic or photographic devices or potential aids of any kind. Note: If you require wheelchair access or need to use an assistive or medical device, please follow the process to request a test accommodation.
(above courtesy
www.mba.com)
Watches are mentioned three times in this not-comprehensive list (watch calculators, watch alarms, stopwatches), so I'd be very surprised if they allowed you to bring any type of watch into the center, even though it's a little vague. I'd much rather have prepared to only use the timer provided on the screen and be pleasantly surprised that they let me bring in my Rolex (or, who am I kidding, Timex) than have prepared to have my watch with me and then feel uncomfortable without it.
Analyst1 - keep giving those Thanks! It seems like a much friendlier place here because of them! Here's one for you...