Yes and I have both ethernet and internet set up at my house... both tend to fail and need to be manualy restarted periodically. And if you have dial up interenet - that can get interupted by anyone calling your house, and I'm pretty sure that has to be manually restarted. And what about a power outage?
Now, would I buy it? Not a chance. I've got nearly $300 worth of livestock in my aquariums - I think I'd rather pay soemone the $20-40 to come watch/feed my tanks then trust the ethernet, internet and power to work, not to mention that it will probably cost atleast $100 + per tank (multiplied by 5). Equipment can also fail as well - can this device of yours restart a filter? or rush to the fish store to buy a new one? Add to that the fact that I don't see the point of going on a vacation longer than a few days and I have no use for this contraption of yours.