Most airframe manufacturers offer forward and downward cameras as a customer option. A lot of the newest planes also have tail mounted cameras that the flight crew can view in case they have a problem that would benefit from an external view of the plane (in-flight engine fire for instance).

I've seen it on some flights, but can't recall the carriers. As other have said, sometimes it is often turned off for some or all of the flight due to the "Abundance of caution" mentality that seeps into everything these days!