Anyway, I am much better than designers at coming up with impossible devices. Can I win an award or something for this? Thx in advance...
(Sarcasm aside, it seems that designers only think about the device. I would rather think about what I want to do, and then do that without a device. Hence being able to travel through time without a screen strapped to a battery in my pocket. That's my goal...)
I will say however that without the (seemingly, given the limitations of their time) unrealistic visionaries, we would not have the technologies that we have today.
Incidentally, they didn't really show any really novel use for the device, except maybe the scene where they use the device to hold a flower temporarily (because you'll need to water the flower if you're planning on leaving it there).