For this purpose, you can get a baby safe mirror which is attached on the back seat and you can keep an eye on it through your rear vision mirror. (newbornbabyzone.com)
Like the time I looked in my rear - vision mirror in a busy Leichhardt street and saw two rabbits shagging on the bitumen. (housegoeshome.com)
This item is dedicated to anybody who has ever vibrated to the fearful thunder of an oncoming truck - trailer on the highway, those monsters that roar up behind and fill your rear - vision mirror with the awesome image of their giant radiators. (si.com)