If lead is detected, a smartphone app linked to the device alerts the user with a color-coded reading and a concentration value that indicates the severity of contamination. A green screen indicates that the lead concentration is below the U.S. Environmental Protection Agency's (EPA) regulatory limits. A red screen indicates that the lead concentration exceeds the regulatory limits.
Making this dependent on an app is a terrible choice. The indication could be accomplished with an LED, no need for a smartphone screen.
Frankly I'm not sure why an electronic device is needed for something that can be accomplished with a test strip.