Yes, two Southwest posts in one day. Sorry. 
Last week, the airline announced its brand new iPhone app, which has actually been around since December, but there was no press release on the subject until last week. My guess is that Southwest wanted to launch it quietly and see if there were any bugs before publicizing it.
Anyway, the features of the app aren’t actually all that different compared to Southwest’s current mobile website, except for the DING! feature. But even though most of the features aren’t new – this is still a good move. Eliminating the need to surf to mobile.southwest.com makes for an easier user experience. And this does have the potential to increase DING! sales a bit.
I do wonder if Southwest will expand its offerings to include other phones. Yes, the iPhone is incredibly popular, but BlackBerry still has a larger share of the global smartphone market, and carriers that aren’t AT&T are busy pushing their Android offerings.
Regardless, mobile is big, and it’s not going away. While specialized apps aren’t necessary, airlines need to make sure that they have offerings that make life easier for travelers with smartphones – it makes life easier for travelers, and could potentially save time for airline staff as it gives passengers the options to take care of travel issues on their own while they’re on the go.
This makes me think…I really need a smartphone. 
More details about the app here.
I’ve had the app since shortly after it was introduced. It works fairly well, but I did notice a few bugs at the beginning that seem to have worked themselves out. Much like you suggested, I suspect they quietly rolled it out to smooth the kinks, and work forward from there. One more example of how smart WN is.