True that it is limited by software to less functionality than a traditional computing device. In the grand scheme of things, though, that definition is rather specific and is less meaningful to people outside our field. The iPhone performs functions far more similar to a computer than to television or phone. For instance, I am writing this on an iPhone. 12 years ago, I would have been writing this on a desktop computer and certainly not a television. The other things i use this phone for - photography and music creation - are similarly not exclusively content consumption activities. So while the device is geared towards that, it can also be used for creation.

I'm not an iPhone developer, but from what i understand you can write apps to do about anything and run them yourself - just not distribute them on the app store.