You need a mobile Android device that can provide GPS data.
To read the diagnostics data from your car, you need a Bluetooth OBD adapter. These adapters can be purchased at affordable prices.
For conducting RDE tests, your car must provide all necessary diagnostic data. The app checks compliance once it is connected to the Bluetooth OBD adapter. As a rule of thumb, cars that do not use diesel exhaust fluid (also known as DEF, AUS 32, Ad-Blue or urea), are not compatible as they do not have an onboard nitric oxygen sensor. If the car uses diesel exhaust fluid, chances are high that it is supported.