I've used it for a week now too. Specifically for sleep, it's good for tracking how much and how deep your sleep is each night, and for encouraging that healthy 8-hour interval we are supposed to get. A couple challenges I see are ensuring the data is accurate coming from a basic mobile phone app (this is no replacement for an actual clinical sleep study), the privacy concern that I would want to make sure the data, especially the sound recording, is absolutely private to me, and the pitfall that it may encourage sleeping as much as possible, perhaps to unhealthy levels, to encourage users to fill that sleep Dex.