I see room for three significant improvements for the game regarding untapped iOS functionalities.
1. Making Elder Sign a universal app would be great. It is not only more comfortable for the user, but seems to be a trend as well. Nowadays, almost all major applications come out universally on all iOS devices.
I do not know how much revenue FFG would lose with this move (I imagine not much, as I do not think that too many people are willing to buy the same game twice), but it would certainly improve FFG's image. Perhaps that improved image would bring in enough new customers to offset the revenue loss of two separate sales…
2. Please add iCloud support; it is pretty standard these days. I would like to be able to store my game progress, saves, unlocked characters, etc. on the cloud. This way, I would not lose anything due to a possible system restore, and I would be able to pick up the same game on separate devices (should it ever become a universal app). I could start a game on my iPhone on the way to work and finish it on my iPad when I get home. This kind of cross-platform communication is pretty sweet and rapidly becoming industry standard. Keep up FFG!
3. Consider supporting Game Center! People love achievements and game points. Plus, it can be a great adverting platform, as people who post challenges and achievement progress within their circle of friends might encourage some of them to buy the game.