You could place the switch discreetly on or around the brake lever, but then you've got wires running down your bike. Neater to affix it to the cable, then you have just a few inches to the brake light. You wouldn't think it, but it's pretty stable and solid with a small zip-tie. Although mine is currently in a box somewhere - I didn't want to mess with it when I put a better tail-light on.

I'm thinking about rigging up a wrist band though to recognize when I'm signalling and automatically light up flashing when I do. I think that would be effective.