Absolutely! Opening QS data through API will make lead to more tools that would enable people to share, mash-up, visualize and otherwise interpret their own data, gamify the QS process and take the movement mainstream.
—————————————————————
Can you express your everyday life in numbers? Can you improve your life by turning it into a game? Follow my personal self-quantification and self-gamification experiment to find out: www.measuredme.com
Quantified self APIs is one of the fastest growing areas of APIs in the last 6 months. I think this will be one of the quickest paths for APIs to penetrate the masses.
After quantified self it will be other home, environmental and auto APIs that developers can use.
They're key just so you can get the data out in the first place. (First law: all non-Free software is a dead end.) You may be willing to copy out data by hand for short one-off experiments, but not when datasets stretch over, say, years, as they will come to do so.