i have an app on my Android phone called quick remote that is able to do the most basic functions (On / Off, ch +-, input plus a few others depending on the model of TV) It also can control Cable boxes and other devices.
Not going to replace the OEM remote and may not get into all the menus depending on models etc, but can be handy. Can also be great if your in a bar and want to switch the input on a TV.
Not what you are looking for (not iOS), but thought others here might find it helpful.