Yes, Tomtom was displayed at the WWDC in June. the link in an earlier post shows the Tomtom page with more info.
AS far as the overheating goes , I feel it may be pre-emptive against any impending legislation. I seem to remember an article about an ipod touch igniting in someones pocket and the legal case that the mother tried to get going.
As the 3GS operates faster with a better processor, Maybe Apple are covering their a**e ?