I have been traveling for the last week in Hawaii, using the TomTom GPS app on my iPhone 4 instead of the dedicated Garmin Nuvi our family typically uses when traveling. I have the Garmin with me, but I have not taken it out once. The TomTom app is that good.
One fear I had was that the TomTom app would require good cell service to be useful. After all, ATT can be spotty and Hawaii is a challenging cell environment with volcanos that tower thousands of feet above the shore. The TomTom app works even when there is no cell service. The entire US map set is downloaded on the device (over a GB).
But cell service does make the app better. The best and easiest way to set a destination is to search near your current location with Google from within the app. That part will only work when you have cell service. You can still enter an address or find common points of interest with no cell service, but Google makes searching much easier. In fact, searching with Google is so much more functional than entering addresses or POIs using a Garmin that often when operating the Garmin, we obtained addresses from our smart phone anyway. Integration makes sense.
The app works even when the phone is sleeping or when you are using a different app and the TomTom app has been thrown to the background. This is important for battery life, since you can sleep the display. We have a car power cord that we use when navigating though.
Since we lack a dashboard or windshield mount for the iPhone 4, we are more dependent on the voice prompts, which are excellent. To be fair, since I am here with the family, we have a dedicated navigator in the passenger seat, which makes seeing the GPS as the driver less important.
My biggest gripe with the TomTom app is that there is no way that I know of to tell it to stop navigating. Hence, you have to go back to the home screen, double tap the home button to bring up the iPhone task manager, and explicitly kill the app when you are at your destination. Otherwise, the TomTom app keeps giving you directions even when the phone is back in your pocket!
Accuracy of the GPS is adequate enough that the TomTom rarely reroutes due to confusion over which road we are on. These spurious rerouting events might be due to map mistakes or GPS errors. My Garmin Nuvi seems to reroute with the same frequency.
I also have a Verizon Droid X with me and sometimes run the navigation systems side by side to see differences (don’t worry, I am not driving when doing this). The Droid X does require cell service to navigate, at least to get the initial map set over the air. But since the Verizon service is better and CDMA carries further, we did not find a single place within Maui or the Big Island where there was no Verizon service. Even at 13,000 feet on the top of Haleakala, where the iPhone 4 reported “No Service” the Droid X showed service. Hence, on Verizon, the built in over-the-air-assisted navigation may be good enough. And with Android, turn-by-turn navigation is built in, no extra app purchase required (expect Apple to address this within 12 months).
I am very pleased with the overall performance of the iPhone 4 as a GPS device. With the TomTom app I no longer need my Nuvi and with the Geocaching app, I no longer need my Garmin GPS Map 60 CSX (although still use it for longer hikes).
If you are an iPhone user and travel a lot, the TomTom app is a good value (although at $49, it is one of the most expensive apps out there) and will assure that you are never without turn by turn navigation. And you get to lighten your bag by leaving home the dedicated GPS.