The iPhone Blog has posted a screenshot of a warning screen that the iPhone 3G produces when it's over heated. According to Apple, it's totally legit. From the Knowledge Base:
"Operate iPhone 3G in a place where the temperature is between 0º and 35º C (32º to 95º F) ... If the interior temperature of iPhone 3G exceeds normal operating temperatures, you may experience [the] Temperature warning screen."Here in New England, we don't see temperatures above 95º F often. Still, I have felt it heat up pretty good after playing music for two hours straight during a summertime commute. It does get cold, however, and two weeks ago we saw a frozen iPod come back to life. It's nice to know that these devices can survive (or protect themselves from) temperature extremes.