The "Barnacle" is a networked car-immobilizer that parking guards stick over the windshield of your illegally parked car; you pay the fine online and the Barnacle gets an over-the-air signal to release itself from your car so you can remove it and put it in a nearby deposit bin.
Except that it turns out to be really easy to remove a Barnacle without paying — some redditors say they can remove it just by running their car's windshield defroster until the suction cups give up.
What's more, once it's been removed, the Barnacle can be opened with a simple Torx screwdriver and its SIM extracted. One user reported that they were able to use this SIM to get unlimited wireless broadband for several months before the Barnacle company terminated its service.
The University of Oklahoma announced that it would begin using Barnacles for on-campus parking enforcement on Tuesday; later that day, it announced that it was canceling the project after student outcry.
U Oklahoma student Sally Johnson published a viral tweet explaining how to defeat the Barnacle that fills me with delight.