This is a fantastic product - very nice hunting!
I'm sure the figures are high, very high, on the number of women who've been drugged with something like a date-rape drug. The crimes often go unreported, or the women isn't sure what happened, so just feels guilty and might never share her story.
So, this product is a real step in the right direction. But I just worry it's not going to fully work as intended.
In a bar, a nightclub, or at a party. where these incidents often occur, the setting is often dark, or the lighting isn't a standard colour. Even though the change in colour on the napkin seems quite noticeable in white light (on a white napkin), I wonder whether it'd be as noticeable in red, blue, or purple light - even light which is changing. This is especially true in a social setting, where you might not be concentrated fully on the napkin (assuming you're safe).
I think an answer to this, and what I'd like to see happen, is that bars, nightclubs and other establishments where women are routinely drugged should [maybe even be forced to] take some responsibility.
If a bar (for example) had to serve all their drinks on these napkins, as standard, and all bar staff had to look out for changes in colour as part of their serving duties, I'm sure you'd see much better results. The bar staff would know the lighting in the place they work, and how that would affect the napkins, and they would be sober and alert.
This is such a great product, I'd really love to see it succeed, But the responsibility shouldn't rest solely on individual women.
RE: KnoNap - Drug-detecting napkin