These questions were asked when Vessyl made the front page months ago.
1. It can't detect date rape drugs. 2. It can't tell if your water is clean. 3. After detecting what you're drinking, it will tell you on average, how much sugar that drink has. Maybe that's useful for diabetics. Not sure. But it's not being marketed to diabetics. It's being marketed to tech people who like tracking things.
BTW, Love "Pencil". Especially this quote: "An artisanally crafted tool. The body is milled from a solid piece of premium-grade walnut that has met rigorous standards for sustainability. Each Pencil has a unique character that will subtly change with years of use."
Ha. Artisinally crafted. Walnut. Stylus.
[1] http://www.fiftythree.com/paper
[2] http://www.fiftythree.com/pencil
Maybe this tech could be extended to create anti-drug cups en-masse for bars, or maybe use it for simple safe-water testing? Or what if diabetics could use it to test for sugar levels? Just speculating, I have no idea how it works though.