These are a great idea which is perhaps new only to the knitting world; Stitchers have been using these or a similar product for at least 30 years, and they've been in use in the Orient for cutting lichi nuts for much, much longer.
Watch a short video about Yarn Snips
Yarn Snips from CocoKnits
A handy tool that looks good, too! From CocoKnits, this yarn snip is a rustic, one-piece tool made of forged black steel and comes packaged in a kraft tube for easy portability and storage. When not in use, the snip sticks to the Knitter's Keep
Please note these are snips, not scissors, and they are imperfectly hand-forged. They have a nice heft in the hand, and the good news is that no one is going to borrow them from your knitting kit – they are really only good for snipping yarn.