How did I never know that a treadmill on wheels existed? It's called the Lopifit, and it's a treadmill and an e-bike all in one!! You can "walk" up to 15 mph on it.
From what've I seen, it originated from the Dutch, but I've seen videos of them being test-driven in Orlando. (See the Lopifit below)
This isn't a paid ad for them, but if you're interested, check out Lopifit US! And if you buy one, let me know how it goes!!