At the suggestion of one of the locals on Maui, this app is well worth it. We used this on the road to Hana and it was spot on. Even when I lost signal, the app continued to work like a charm, giving commentary on the most noteworthy places to stop, along with some of Mauis historical information. Dont your the island without it. Its much cheaper than hiring a tour guide!
Kimmal about Maui GyPSy Guide Driving Tour