Researchers say we don’t put on enough sunscreen. A Seattle startup has come up with a potential fix: an invisible ink stamp that notifies you when it’s time to re-apply. Michael Croix, a longtime ...

A few years ago, [Mitch Altman] from Noisebridge came up with the idea of a Hackerspace Passport. The idea behind it was not to hinder or monitor travels but to encourage visiting other hackerspaces.

People use document stamps to mark documents quickly with information relevant to their creation, distribution or storage. Information stamped on, or embedded in, a document can relay the time and ...