The Verge did a nice episode on fitness and health tracking devices in their Top Shelf series last week. I think it gives you a pretty good overview about what is already possible today in this area of technology.
I am personally pretty fascinated by this stuff as it will eventually help us to make better decisions about our health, eating habits and general fitness. The collected data also will help doctors with their diagnosis as you can basically track your whole day with using the different devices.
As stated in the show, there is still a lot of work to be done. Currently, it’s pretty much up to the individual person what to do with their data, the companies only provide your with graphs and statistics. Building an API all the different manufacturers could use to make better use of all that data would benefit us customers too. Nevertheless an exciting trend.