The Ping app is a graduate project from Kristian Knobloch that serves as a "digital and interactive guidebook" for hosts and guests on Airbnb, according to the Ping website. The Ping app and modules combine to form a system that makes using the sharing economy easier for both sides of the housing equation.
Essentially, Airbnb hosts can set up modules around their house or apartment and, using the Ping app, they can add information to these modules. That might include something as simple as a reminder to feed the cat, something as complex as detailed instructions on how to feed the cat, or something interesting about the house, like how many cats have lived there.
When guests stay at the house, they can then tap their phones against the NFC-equipped modules to gather information and make their stay easier and more pleasant.