I would assume the opposite -- although, unlike you, I'm not an elite competitor, so I don't really have anything to lose if I'm wrong.
I would hope that after the lengthy discussions here on AP about the benefits of post-race GPS analysis, as compared to the remote possibility of using a ForeRunner for a cheating advantage, that the rules will catch up with the technology.
USOF rules state:
36.3 During the competition only a compass and the map provided by the organizer may be used for navigation.
36.3 Personal aids not used directly for navigation are permitted. (e.g. magnifying glass, flashlight, cane, eyeglasses)
36.4 The use of any navigation aid other than a compass is prohibited. (e.g. transport, electronic apparatus, radio, pedometer, altimeter)
[Citation courtesy of jjcote]
So, if *I* were in charge, just having a ForeRunner passively strapped to your arm during a meet would be fine, as long as you didn't use it to navigate (just as you would not use your cell phone, or wristwatch, or heart rate monitor, or a map from an earlier runner, etc., all of which have been discussed
here and
here...).