these are the 'gravity ruler' luggage scales, by politecnico di milano students marcella maltese and lin wei. you wonder why no one did it before. for me, it's another one of those 'i had that idea a few years ago' kind of designs. not to take anything away from it though, this is such a good design; so simple and so effective. the packaging is great too!
from the original article:
The demand for these things (what with the miserly 15kg allowance on Ryanair flights in Europe and the clumsiness of other similar products) was proven when the pair sold their first batch of 35 in under an hour at the Travel Trading fair in Milan. They're now looking for a manufacturer.