Contraptios like that are pretty common for goldfish with buoyancy problems. I have never had to make one, but I have friends who have. Hand-feeding is also pretty standard with fancy goldfish keepers. This is especially true if you are keeping different breeds of fancy goldfish together. Plus, it's a fun way to interact with your fish.
The biggest problem with those wheel chairs is the rubbing against the scales and slime coat. Just like humans get bed sores, goldfish can get sores where the harness rubs against the fish. Often times this is what causes the fish's down fall. I don't know about that case specifically, but I'd heard of other cases where the harness has extended the fish's life about a year.
Either way, it's heart-warming to hear someone cares that much for their goldfish. I'm glad to know I'm not alone. :)