Let the hive mind of Engadget get that for you.
"As someone who doesn't reside in the USA, I was wondering what would be the best way to get internet for my computer in the US for a couple of weeks? If it were Europe I know I'd look for some prepaid data. Is there anything similar offered by American carriers? A MiFi or a data SIM that I can tether from would work, but I'm trying to maintain a tight budget. Help!"
Joel A. is correct: actually, BMW was not the first factory system in the U.S. to have this. Cadillac has it in the CTS using XM NavTraffic, which they launched 2005 model year. Can't say whether it works well or not, just that they were first.
MK and G.Snyder are correct: 2005 to 2007 Acura RL, while it has XM NavTraffic (what some might call "dynamic" or real-time traffic), does not have dynamic rerouting (also known as Dynamic Route Guidance).