Developing a mobile app would allow you to take advantage of the user's smartphone features such as geo location and camera. This is why companies such as Foursquare and Foodspotting opted for a native smartphone app. However, if the intent is just to provide users with information then a mobile friendly Web site will do since that will work on any smartphone platform. Take a look at your sites Web analytics and see how many current users are trying to access the site with mobile devices. This may help you determine if you should develop native smartphone apps for iPhone, Android, Blackberry, Windows Mobile, etc.