AWS SC-2KGA Digital Pocket Scale (w/ adaptor)

This handy little scale offers excellent speed in registering weight, it's the perfect weight capacity for any home brewing methods (from a large French Press to a Kalita or AeroPress), and it measures down to the tenth of a gram.

Plug it into the wall when used at home or toss in AAA batteries and pack this slim, tiny scale when you want to brew your specialty coffee on-the-go.  

For those of us that are especially groggy in the morning, it even has a blue backlighting as it registers an increase in weight. 

More about this coffee

In all seriousness, if you brew specialty coffee at home, you should have a scale.  Coffea suggests 16 grams of water for every gram of coffee.