Bottom line: Not worth it.
It’s a nice idea: pocket-sized gauge which screws onto the valve threads of the fuel canisters and can give you a percentage of fuel left for the three sizes of canisters (100, 230, and 450 gram.) It can also give the total weight in grams.
Unfortunately, I have found it unreliable: weigh the same canister multiple times in a row and I’ll get different percentages. Not just 1-2% different, as much as 20%. It also went through a CR2032 battery in 3 months when it was off for 99% of that time.