Interesting early stage announcement From onelvl (BSX Insight).
A hydration monitor wristband which, from the image, clearly looks to be able to show heart rates too.
If you participate in endurance events over an hour you will know how important it is to keep a good level of hydration.
The starting place for that is to know your current hydration level.
More details will follow no doubt. Nice idea. One of those ‘obvious in hindsight’ ones. The best kind.