I have thought a lot about this concept of using a smartphone app to replace some physical components of a game, and I'm surprised more games don't do it. On top of being less cumbersome, using your phone would allow for some mechanics that simply aren't feasible (or even possible) with physical parts. The flip side is that you have to "sync" the app state with the state of the physical board, and you need a clever solution that doesn't require doing things twice. (Plus, I'm sure some would argue that having parts of the game be digital would take away from the immersion, though I personally disagree.)
The problem with this is that it's very easy to get stuck with a useless board game if the app doesn't get updated.
If you're selling physical product that needs an app to run, there is no reason for the app not to be Free Software, or distributed in some other friendly way (e.g., Space Alert has a CD-DA disc that plays the scenarios as audio).
I've seen more and more games do that, from XCOM and Space Alert, which mostly use it to provide randomness and a timer to Mansion of Madness, which is mostly facilitating exploration.
Those games work well, but for me, I wouldn't want to play a board game that leans on an app any more than Mansion of Madness; at that point it's a video game, and while I enjoy those, it's not why I play board games!
