The stuff in their video doesn't make sense:
"Ever notice how some of your electrical appliances give off heat [woman seen noticing heat coming off the top of the TV]? The Power Save 1200 supplies you appliances with just the power they need, and no more!"
That doesn't make sense to me. The TV gives off heat because of inefficiencies in the electronics, and changing the power to that TV isn't going to fix that.
They show a toaster in their video. Above explanation not relevant for a toaster, unless you want it to heat the toast less.
Finally, it would be very easy to measure the effect precisely, but I don't see that.