They say they don't listen for watchwords and only record video on demand. Good.

But that means their hypothetical calorie-count example only works if you actively remember "I am eating, I should tell the pin to record my eating". Same with many other things; the wrist-worn smart devices are useful exactly because they are always recording, they are somewhat ambient.

I understand why they do it, I even applaud them for thinking about privacy, it might even be necessary (cough..Google glass...cough), but I feel they have to walk a tightrope between a rock and a hard place to bring privacy-consciousness and useful features together.