This is one of my all time favorite German style board games to play. The mobile pocket versions is totally free right now. This is an award winning app. This is perfect to whiling away time on your holiday travels for yourself or the kids. I love that you can opt to play locally over wi-fi or bluetooth so that you can play with whoever you are hanging out with.
I love that Ticket to Ride engages you in thinking strategically since you are not building routes in isolation.
Recommended ages 8 and up.
ETA: Be sure you are looking at iPhone apps on your device.