In planning our trip to Hawaii, our friends recommended that we download the
Shaka Guide app for the Big Island. It is an audio tour guide that uses your phone's GPS to automatically play the segment that corresponds to where you are, complete with turn-by-turn directions, suggestions for places to stop, and even music for traveling in between points of interest. There were five tours covering different parts of the island, so we bought the whole bundle for $9.99.
Our destination this morning was Pololū Valley on the northern tip of the island. The drive along Queen Kaʻahumanu Highway was gorgeous! The Kohala Coast tour audio kicked in once we passed by the resorts at Waikoloa. The tour narration was really interesting, and the app worked well (offline, so no cellular data needed) - totally worth the price paid!