Navigon's maps look good and the additional in-app purchases include realtime traffic information, photo-realistic depictions of junctions, 3D panoramic landscape rendition and U.S. radar information.
While I'm on the subject of maps and car travel there are two more apps that you'll want (I use both of them mostly on my iPhone). The first is called Waze (pictured at right), published by Waze Inc. Waze describes itself as "social GPS traffic and gas" and claims to have 20 million users.
What's so cool about Waze is that it provides routing (with voice prompts) and, using realtime traffic flow measured by speed and location data from Waze users, can re-route you to better routes to avoid slowdowns and other problems.
Using the Waze voice control interface users can also file reports on accidents, hazards, police traps, note gas prices and even get cheaper gas from stations participating with Waze. On my trip I had several warnings about police traps (such as around King City, Calif., where many of us have, at one time or another, been nabbed for over-enthusiastic velocity) but they were usually ten to twenty minutes out of date.
Waze supports community building so you can form groups to share, for example, your thoughts on your commute with fellow sufferers. There's also a "meet up" feature to enable friends to coordinate getting to a common location.
The other app that you need is INRIX Traffic (pictured at left). A big question that INRIX addresses is "when is a good time to travel to X?" For example, you might be in Saint George, Utah, and think that driving to Los Angeles via Las Vegas at 1 a.m. on a Sunday would be pretty painless ... but, and I speak from hard-won experience, you would be wrong as it will add at least another two miserable hours to your drive. With INRIX you can set your route and then see what the best window for traveling will be in the next 12 hours!