Are you asking "why mobile", or "why native, as opposed to HTML5?" The answer to the first question is obvious, IMHO. I always carry a mobile device, whereas

Are you asking "why mobile", or "why native, as opposed to HTML5?" The answer to the first question is obvious, IMHO. I always carry a mobile device, whereas I'm only at a computer 12-14 hours a day. As to the second, opening a web-app using a mobile browser is cumbersome and thus a fairly large barrier to adoption. The key to this app's success - as with any personal analytics tool - is continuous use.