This isn't for everyone, but we didn't use any sort of camera or mirror until my son was a little over a year. The risk of them becoming a projectile in an accident and causing a distraction to the driver were enough for us to not use when he was little little. I don't even remember why we ended up getting a mirror, but we got a super cheap, flimsy lightweight one when he was older.
I don’t want to scare you but I learned from a car seat safety tech that they are not recommended because of the dangerous of them becoming a projectile in an accident. That’s why car seat manufacturers don’t sell them as add ons.