We always recommend that drivers have access to and use navigation that is built-in or mounted in the vehicle for best road safety.
If the vehicle is missing this option, it is still possible to use the map function from the phone. For Android, you can choose any map feature while iPhone allows its own Maps feature Apple Maps. Other navigation apps on iPhone also work, but without the full visualization...you will only receive sounds and notifications.
Any custom apps for your service can also be made available for Android phones to use while driving, just let us know!
Remember that the phone should be positioned so that the driver can focus on the traffic and preferably use the voice control function so that driving directions are given via sound, for best traffic safety.