Transforming an old tablet into an Android Auto head unit involves activating developer mode and enabling "Unknown Sources" to sideload applications. Alternatively, third-party tools like Android Auto Apps Downloader (AAAD) can be used to integrate unofficial apps. Sideloading carries risks, as these apps are not officially vetted and may malfunction after system updates.
CarStream is a sideloaded app that allows users to access YouTube on their car display without rooting their phone, making it useful during parked moments. Fermata Auto is an open-source media player that plays local media files from a phone or hard drive, ideal for offline use. Screen2Auto mirrors a phone's display onto the car screen, allowing access to any app, but should be used with caution while driving.