I have not seen the advert, so please accept my post with that in mind, but I have grasped the principle behind it.
In a person who is inactive for whatever reason e.g after an operation or with rheumatic disorders, the blood can "pool" into the muscles of the foot leading to stagnation, poor circulation and perhaps DVT.
Now, this does not happen with the vast percentage of people as they tend to be mobile and the muscles of the foot propel the blood from the foot back, through the legs to the heart. The machine described almost certainly produces small electrical charges which cause contraction of the muscles of the foot urging upwards normal blood flow.
The circulation to the leg has a flow of blood from the heart to the legs....Arterial side.
A circulation of blood from the foot to the heart......Venous side.
If your problem is on the Arterial side, then the machine will be of NO value.
If your problem is on the Venous side, then the machine will help post operatively, but of doubtful value otherwise.
In my opinion.