On the downside, sleep tracking requires manual activation and the band that houses the actual «bit» can be uncomfortable if worn for long stretches. (moneysense.ca)
According to Francois Beaufort, a «Happy Evangelist» at Google, a «quick lock» function is currently in testing and requires manual activation of a Chrome flag to test it: (thenextweb.com)
Premium Subscription (Royal Blessing) requires manual activation from your items chest. (1cshop.eu)