We used the Shaka Guide tour app while on the island of Kauai. We've previously used Rick Steves tours in Europe, and I wish that Rick Steves had the autoplay-based-on-location feature that this app has. It's fantastic. There are 4 Kauai tours and we chose to do 2 of them. We chose the waterfalls tour on the east side of the island and the Waimea Canyon tour. Both were great. The only better thing that we did in Kauai was to take a doors-off helicopter tour.
PROS:
* The tour is timed based on your location. No starting/stopping or fast-forwarding is required.
* The stories are interesting and relevant to the tours.
* The app helps you find interesting hikes with amazing views, including details about finding trailheads.
* Download the app data to your phone for areas with slow or no service, which happened in Kauai.
* Great for local tips, such as restaurants and views.
CONS
* Shaka guides are only for Hawaii. I would love (and will look for) something like this in other locations.