Bil og henger, developed by Statens vegvesen NPRA, is a free Android app designed to provide users with an easy way to keep track of their registered vehicles and trailers in Norway. The app offers a range of features that make it stand out from similar apps in the market.

The app allows users to view registered data about their vehicles and trailers, check which trailers they can tow behind their cars, and save all their vehicle and trailer data in the app for quick access. Additionally, the app sends alerts when the deadline for EU inspection approaches. The app also provides a feature to check the owner of the vehicle, which can be accessed through Din side login or SMS service to Statens vegvesen for a fee of kr. 3 per search.

Note that the trailer calculator feature can only be used for trailers that require a driver's license for a car or a car with a trailer, and not for heavy vehicles.