This may sound like a dumb question, but I was curious, for anyone who has ever used training tubes for baseball or in general resistance trainers for improving velocity, are they basically the same things as bungee cords? In theory, could you use a bungee cord attached to something and pull on it to imrove your arm velocity?

In theory yes, but, the tubes are designed to have specific resistance so you can build up...not pull your arm out...the one they sell with a ball attached is great...especially when it is raining and you can't go out and throw!

do not use bungee cords they have what we call not enough resistance i mean you could but that is not what they are for and they are not as good

Theoretically yes, but dont use them.
Im a pitcher and i love the training tubes.
They improve arm strength, velocity and reduce the risk of injury.