In past posts I have ranted about the challenges of developing applications in the mobile space: the closeness of various platorms, the fragmentation of devices (ranging from hardware to operating systems to development platforms, and even to applications, such as browsers).
Today, even as I anticipate the blossoming of open platforms, I still strongly recommend SMS as the simplest and fastest way to reach mobile users. This is why I was ever so delighted to see that TechCrunch's first "Best Mobile Start Up" Crunchies award went to Twitter. I am a huge proponent of Web meets Mobile services; in a not so far future all applications will fall under this category.
It is true that Twitter is more than a mobile application; it integrates many communication mediums. But when it comes to taking the best it has to offer, its simplicity, and taking it to the next level by integrating mobility, Twitter is still one of the best examples I can think of.