First up, the concept is great and when it worked it was fantastic. Loads of useful information, interesting stories - just what you'd hope for from a first rate guide on a private tour. The Shaka Tours narrator is a little hokey (which took a little getting used to) and it was a relief when we figured out how to turn off the background music. There's only so much ukulele music you can take. I have nothing but praise for the information and tales provided.
BUT using the apps was a fingers in the eyes, frustrating experience.
1 - Mostly the tours run only one way, So, if you are staying in Lihue with a first slot of the day visit to Limahuli you can't run the tours clockwise. So annoying. I feel that this is the makers cheaping out. The content would be the same, it just needs running as a pair of apps. (Manually running the buttons was awful because many steps are a leading on to the next stop so it gets confusing really quickly.)
2 - Where you have crossing or looping tours the app gets confused and will flip you between legs. Wildly confusing as right becomes left and as you are 'trusting' the app you can quickly be baffled. On day one we learned to run Google maps on our other phone so we knew when we'd been sent wrong. The method of previewing the route is awful. Hard to get into, and zooms in and out depending on your activity state.
3 - The turn instructions are really dicey. They rely purely on GPS location (it would seem) so you get something like 'Turn right here" - which if you are on a 50 mph road in busy traffic may not be safe or practical. And keep in mind it will at times flip left with right as it seems to lose track of your direction. And joining the tours (we used 8 in our two week vacation) never worked once. Both these issues would be easily solved by just adding a little more information - it knows where you are - so, saying "Turn right just ahead by the mailbox (or whatever)" or join the tour at a fixed place - "Start the tour outside Safeway (or whatever)" would be so much easier.
So, it it worth it. Yes. Would we buy it again. Yes - we bought one as a trial, then the rest of the bundle, then bought the Big Island bundle.
Could it be better - oh, boy, it sure could. Bring your patience.