A Tokyo taxi company has hit on a solution to the all-too-common problem of passengers leaving items behind. The Wall Street Journal reports that Kokusai Motors plans to implement a camera-based system which sounds an alarm when a passenger forgets to take something out of the vehicle. Four cameras figure this out by capturing and comparing images of the back seat before and after the journey.

Kokusai Motors will reportedly install the new system across its entire 3,100-strong fleet at a cost of around ¥50,000, or $500, per car. 210,000 forgotten articles were reported to Tokyo police last year, according to the Journal, and Kokusai Motors says about 60 percent of those found in its cars are mobile phones.