Caution: This Cart Will Stop Suddenly If Taken Beyond The Yellow Line

Recently, I saw this sign in a shopping center parking lot while picking up a prescription. Thinking that no way this was true in this particular lot, especially since it was a standard shopping cart with no "accessories" on it, I had Kris push the cart past the line, and suprise,suprise....it didn't stop, it kept going! I'm sure these devices exist especially in more urban areas, but not in this parking lot.