Mine isn't exactly a streamside innovation, but it was created because of a streamside problem. One morning, my fishing buddy, after tying on a tandem rig with two flies, discovered that he forgot to put his strike indicator on. (He was using one of those little hard foam ones with a hole and a toothpick--they are commonly called "Lightning Strike" indicators around here) He asked me if I had a knife or something, and I said no. He said that he wished that his indicator had a slit in it, so he could just slide it on. So, he cut off his tippet and started all over again. That got me thinking.
I went home and made a little saw using a 2" wooden dowel, a piece of a coping saw blade, and Gorilla Glue. Voila! I put this in my vest. Now anytime I buy uncut indicators, all I need to do is grab my saw and slice into them.
It works for me.