This is part of the XM Satellite Sytem. It's part of your free subscription if you've activated it. They activate all channels, Weather, and Traffic.
The weather is ridiculous - all I ever get is high wind and flood alerts. Nothing else. And the traffic I have found to be useless. I was in dead stop traffic the other day and pulled up my nav map - it had a solid green line on it. They just don't update often enough. I kept my XM subscription but cancelled both Weather and Traffic alerts ($45 each per year!)
I thought the same thing on our recent trip regarding the flood alert especially since there wasn't a cloud in the sky however 15 miles later we drove over the Ohio and MS rivers and they were both flooding. No impacts yet to the roads but down in MO/KY areas they are starting to flood again. Anyways I guess it works. Also while in DC we received a warning for Gale winds and no kidding 10 min later it got very windy!
Regarding the traffic it definitely showed issues when we were in DC and then traveling through Knoxville and Nashville. I have no clue how often it gets updated however both cities were exact when we drove them regarding the slow and stopped traffic flow. Also on one stretch of highway it showed bridge construction in several miles and offered a detour. I zoomed into the area and saw the traffic was green so elected to stay on the main highway. The construction either wasn't there or just wasn't affecting the traffic at the time. I also noticed in one of the menus for navigation you can have your route based on traffic history and/or real time.
Anyways we bought both services for 1 year for $82. It was a pain since our radio has lifetime service that was transferred from our other vehicle. It took XM forever and several days on how to activate the WX and Traffic for a lifetime radio. They finally got it figured out but I'm not sure if I'll keep it next year.