Home FAQ Is the OnStar Guardian app the same as the myChevrolet, myBuick, myGMC or myCadillac mobile app? No. The OnStar Guardian app is a new app that gives you access to critical OnStar safety services through your smartphone in any vehicle and virtually anywhere you or your loved ones go. Previous When a crash is detected, who does the OnStar Guardian app alert? Next Is the OnStar Guardian app still working if I don't see a notification on the app?