A lightweight backpack that is completely untouched by all kinds of difficulties and weather changes.
A scooter / suitcase that helps you cross those long corridors in airports.
A very useful gadget that only very few travelers will ever use.
A piece of luggage only suitable for a few personal items, with its functionality being mainly to carry other pieces of luggage.
It may seem easier and less expensive to spend only a few money and buy a small carry-on bag, but a more expensive, more gadget-y bag will pay off a lot more than a cheap one. Like it happens with every item, you get what you pay for.