The following is a direct quote from an old Rhizome article:

Off the record is a punctual underground underway art show that takes place at various venues and subway stations in Tokyo. It hijacks the recently installed X-CUBE© locker system. X-CUBE© lockers allow multiple users to exchange packages by using a touch screen and their cell phone numbers as digital-keys. Proposed by Belgian artist Eric Van Hove, the tactically curated Off the record exhibit simply substitutes the package with an artwork or installation.
Existing entirely in transitional public spaces, the show nevertheless remains hidden and visible solely within a private network: a person who has gained access to the work can only invite someone else to view it whose cell phone number they already have.

I like the idea of art in a coinlocker that you have to be invited to look at. It's kind of elitist though maybe?