One of the big pains in the ass with having an FM transmitter to get music from your iPod/Zune to your car radio is finding a clear radio station. A frequency may be fine where you live, but drive 20 miles in any direction and it could be totally packed. DLO's OpenFM tool lets you search by city or zip code and gives you the best (most open) frequencies in the area to tune your FM transmitter to. And they're hoping that you buy a DLO FM transmitter while you're there. It even has an iPhone-customzied version. [DLO]
This would be truly valuable if you could plug in your route for a trip and have it give you a list of frequencies to use along the way. For instance I'd love to know the best sequence of frequencies to use from your above demonstration of San Mateo to Truckee, CA.
Can anyone make a mashup of that with either Google Maps or Microsoft Maps?