ride shotgun

Short definition from Wiktionary

Verb

1. 1
   To accompany the driver of a vehicle on a journey as an armed escort (originally with a shotgun); (by extension) to accompany someone in order to assist and protect.
2. 2
   To ride in the front passenger seat of a vehicle, next to the driver.
3. 3
   To supervise a process and watch for any risks.