I'm pretty sure I know what this is before even replying...but in the chance that it isn't, what kind of convenience are you looking for that would require software of some kind (assuming you mean something you add to your computer that makes the iPhone more "convenient" as you put it)?
If you're talking apps on the iPhone itself...your question is just way too generic and you could really stand to check out our app section of the forum for general "what should i download?" type questions.