The basics:

Invented in 2017, the PathSpot HandScanner can detect the presence of contaminants on the user's hands. The device mounts on a wall near handwashing stations and allows food service professionals to check the cleanliness of their hands before returning to work. Users are given real-time feedback on the quality of each hand wash, and the device collects data on the frequency and effectiveness of handwashing so the team can monitor, measure, and improve handwashing compliance.

From the BOH TipJar:

The 2 second scan provides instant results, saving employees crucial seconds in the kitchen and on the floor of the restaurant. Also, if a contamination is detected, team members are directed to rewash and re-scan before returning to work, helping ensure complete cleanliness.

In their own words:

By allowing food service professionals to check if their hands are pathogen free, PathSpot devices not only catch contaminations before they happen, but also train kitchen staff to be better handwashers — on average, PathSpot users see a 60% decrease in contamination rates in just one month.