On my prior coach I used a boat windshield mountable ski mirror so I could keep an eye on the dogs while we were rolling. That rig had the rear view mirror replaced with the backup camera monitor.
I didn't mount it to the windshield but modified a mount so that it connected to the overhead bunk.
I used a mirror similar to this
Gladiator Tournament-Style Boat Mirror - Overton's
On my Class A, due to the depth of the dash board and the distance from the seats to the windshield I believe a mirror would be useless unless it was in some manner mounted closer to the driver's or passenger's seats and not on the windshield.
I having been thinking about mounting a mirror on a swing or telescoping arm to the lower side of the over dash cabinets or to the overhead bunk just so I can investigate which cabinet my wife left open when we roll away from a rest stop.