When designing your applications, always make sure you capture the context and the user's intent - capture why they are entering particular data or performing a particular action. Without the metadata to capture the context and intent, the raw data will be much less valuable.
I recently started training again. I was a competitive swimmer for most of my early life, but haven't seriously trained since then. Being the true geek that I am, I wasn't about to do embark on this new journey without the proper apps.
For running, there's Runkeeper. For swimming, there's Swim.com. For weight training, there's ... no idea. There are too many horrid apps to weed through.
What I want, and haven't found yet, is the ability to merge all of the data together into a single place. This should be a solved problem by now. It seems as if consolidating workout data can be done with a few key integrations. Why hasn't it been done before?
While some of these apps have (incomplete) APIs and offer (limited and delayed) data exports, not all of them do. When you do get the data, it is nearly useless.
The app's data is useless because it doesn't include context - it doesn't include the user's intent. The app knows the intent of the behavior represented in the data. The app knows what the data means. Runkeeper knows that this morning's run was workout 6 of 20 in a 5k training plan and not actually me being chased by a bear. Swim.com knows that GPS is useless for swimming and measuring swimming distances in miles is silly.
Underneath the hood, most apps store the same raw data. It's the metadata around that data that makes the data valuable. The raw data itself is a commodity.