What about the problem? Can it be partially solved without a smartphone? Can it be partially solved by a smartphone using its browser? What smartphone systems actually solve the problem versus providing a basis for additional features?
For example, geolocation makes it easier to review a restaurant, but it is not necessary in order to do so. Access to the user's contacts makes it easier to send people messages, but it is not strictly necessary because typing the information in is an option.
Another way of looking at it is the difference between solving a problem (possibly using a smartphone) and writing an app. Writing an app has a lot of tail wagging the dog...getting through the review process is just part of it. The second part is getting people to notice the app...all apps on the app store are presented in a standardized format. That's great for Apple and Google. It's great for lousy apps because they look pretty much like good apps. It is terrible for any good app with a story to tell, because there is no way to tell that story.
