TomTom Navigation Software for iPhone
TomTom, Europe’s largest Map Maker is now offering Thailand Map with turn-by-turn voice navigation for the iPhone. As the map is installed right on your iPhone, you can use it as a GPS navigation device without having a data plan or even a sim card inserted.
I tested it during the last few days between Rayong and Bangkok (in Bangkok as well) and it works better than the Chinese Navigation System built in to my car.
It recalculates ways faster (tested on iPhone 3GS) and finds much better ways even compared to Garmin GPS devices.
If you receive a call, the device will still tell you the way. But if you have to place a call, you need to exit the software first (due to lack of multitasking). If you finish your call and startup the TomTom software again, it will continue where it stopped before. So no need to re-enter destination etc.
An in-car Mount is highly recommended to be placed near the windshield to ensure you have a steady signal from the satellite. Also you need to have a car charger as it drains battery quickly (without charge the battery will last not more than 2 hours).
You can also download Maps for other Asian Countries, Europe, USA and Canada.
You can download it from the iTunes AppStore for US$59.
Just search for TomTom