I have one on my mirror like @PeeBee linked to, & have zero problems with it. Stays in place, doesn't droop, doesn't move around on corrugations. Without going out to check, I'm pretty sure I removed mirror glass from my mirror (what use is a mirror in a ute with a canopy?) to reduce the weight, & may have tightened up the ball joint a little. Just seems like a normal mirror to me these days.

Important thing for always on is to get the right camera. Narrow angle of view gives best depth of field - use a standard 90 degree+ reversing camera & vehicles approaching from behind will scare the crap out of you when they suddenly appear right up your klacker 'out of nowhere.

I have a 60 degree camera but when it needs replacing will get a 30 degree. 60 degree is a reasonable compromise for rear vision & reversing, but best to have dual cameras - separate for reversing if you need one.

Do not get a CMOS camera, get a CCD - the image you will see in the monitor is chalk & cheese between these two types of sensor. Also the bigger the sensor the better.

For 'always on' rear vision - this is the camera to get https://www.nassecurity.com.au/30-vi...ew-camera.html (& what I will purchase next time).