In the last three days I have driven through some hellacious weather. But my iPhone's "RadarScope" made it like flying a Boeing 737 with sophisticated on-board weather radar. It is the coolest "APP" I've encountered - so far.
In a nutshell, I plug the iPhone into the DC receptacle (cigarette lighter hole) and ride with the iPhone in a cup-holder cradle. I go to "SETTINGS - GENERAL" and disable the screen time-out. Then, I select the RadarScope icon.
I can then click on a small blue icon to mark and track my truck's position (through the GPS function of the iPhone). That overlays on the radar weather map AND a highway map. Another button allows you to pick the radar site feeding the "RadarScope." So you can actually look at weather ahead to plan your trip in near-time.
It was tested to the max today as I left Dallas - in severe weather - headed to Childress, Texas (short of Amarillo). I watched the weather ahead in anticipation (at least in a B-737, I could turn). I could see the heavy areas, and the red boxes for tornadoes. If a red box (Tornado Warning) had overlayed my route, I could have stopped or sought shelter. That is worth the price of the APP.
What a great advantage on the road! Given the higher than normal levels of severe weather nationwide, I'd recommend setting this app for your own use.