What an interesting idea.... ok guys, have the dishes clean and the rugs vacumned before I get home! Nope, I don't think it's gonna happen! :(
I used a round buster cube for mine when they were teething and filled with energy. I filled it with their morning ration of kibble with the opening rather small and then I would put them in their crate. They would push it around getting all the food out and it took them a good 1/2 hour or so. I actually did this even when I was home. That's about the only job they had when I was away other than sleeping! I'm interested to see what other jobs people give their dogs when their home alone. :D