They're becoming pretty commonplace. A friend runs a farm that uses them. The cows come in to be milked when they want to be, which averages about 2.2 times per day, they enjoy getting milked. A back scratching machine gives them a rub (which they love) and they stroll leisurely back to their paddock to eat more of their favourite thing; grass.
Staffing costs are much lower along with the subsequent disasters and animal problems caused by thoughtless staff. The cows are happier than ever and milk production is record-breaking.
I remember seeing DeLaval say that the back scratcher is their most popular product --- among both humans and cows!
Their corporate website looks a bit threadbare (last update 2015), but their Youtube channel has recent videos; I hope they're doing all right, but their products look amazingly cool.
Staffing costs are much lower along with the subsequent disasters and animal problems caused by thoughtless staff. The cows are happier than ever and milk production is record-breaking.