You know the great thing about software features:
YOU DON'T HAVE TO USE THEM IF YOU DON'T NEED THEM.
ok I'll say it....big deal. goofy little gimmick app. I could see using this hardly ever. we don't need more excuses for people to stare at their stupid phones instead of, you know, like actually enjoying the flight and looking out side. not to mention the more people look down at their phones the more likely they'd be to get queasy. if you really want to add something useful to the app to make it helpful, show traffic on the passenger app. otherwise, meh.
if someone expressed interest in taking a flight but really getting into the nitty gritty technical details, I'd have them download the actual app (in my case garmin pilot but it could even be FF) since they get a 30 day free trial. then they'd have a shtload more info to look at.
Are you married? Does your wife fly with you?
I am, and mine does. And I did put regular ForeFlight on her phone once, but you only get one 30-day trial, and she had no interest in seeing aviation charts, or learning how to use the app. She just wants to know "When are we going to be there?" and while I'm happy to answer that, she often asks me at inopportune times.
In addition, passengers would need to make sure they had the proper data downloaded and "Packed" to access in flight, and the pilot would have to share the flight plan with them manually, and they would have to set up the HUD with an ETA display and such... The Passenger app requires no knowledge or setup effort, it just serves its purpose very well, and in a much smaller package than the full version of ForeFlight.
Take your iPad/Foreflight device with you. That's what I do as it's already on my phone.
I do that on airline flights too, but I have to look up the flight plan in FlightAware prior to flight, and I don't get any updates to the flight plan en route, unless I manage to have a handheld radio and keep up with all the frequency changes so that I can listen in.
If Boeing was smart, they would add this functionality directly to their airplanes, now that they have ForeFlight. Maybe there could be "United Channel 9" style ATC audio streamed as well, as long as the user hit a button accepting that they cannot complain about anything they hear in it, and they're permanently banned from ATC audio streaming if they do.