I do not think so. Actually, as mobile web experience improves, mobile websites could very much kill mobile apps. It will take a few years at the minimum though because the experience is a big hurdle at the moment. In theory, the more avenues you have, the more traffic you get. But in practice, I feel that a focussed approach works best. It is sometimes easier to get mobile app only products more traction that websites because of these factors:
1. Experience- it is easier to get the experience right on one medium.
2. App store Optimization- Search engines and socia... (more)
Not very since the market is more than crowded with activity tracking apps and the native codebase provided for this is pretty extensive. My thoughts.