That was King Size Homer where he was working from home because he was overweight and asked Flanders how the rat race was. Flanders said "a crazy guy shot a bunch of people and the subway ran over my hat!"

A company called Virtuix already developed a treadmill like this called the Omni like 10 years ago. They have released a few home versions of it and some larger ones for arcades. They're still refining it for mass production it seems.