This would be useful. I think the reason they stop has to do with chunk loading, which I believe is already being looked into. The ping command would have to give a list. It could get pretty long(I usually run eight) with no real way to immediately tell wich are stoped. I’d imagine it might cause lag. Still it would be nice.
An in game item that did the same thing could also be cool for immersion, or at least some way to track them.