Travel Utility Scale

"Luggage that exceeds airline weight and size limits can cost you a fortune in surcharges."

From the website:

Souvenirs purchased en route may add significant weight to your luggage on the trip home.

Avoid expensive surprises by packing the handy Travel Utility Scale.

Just hook it on your bag's carrying handle and lift it off the ground [if you can] for an accurate weight reading in pounds and kilograms (up to 50 lbs./23 kg).

Built–in tape measure lets you determine if bags or packages exceed carry–on or check–in dimension restrictions.

Also useful for impromptu "guess what the bag weighs?" contests while your flight is delayed.

You could even set up your own boarding gate–side business if you were really mercenary.

Measures 4.25" x 4.25" x 3"; weighs 6 oz.

$9.85 here.