How about the part about "taking one hand off the handlebars/brake lever"?

I don't worry so much about front signals because I can easily SEE what cars in front of me are doing. I kinda like the idea of rear signals, but so far I haven't seen much available that looked sufficient.

Check Google, there are some light kits available--some also include a brake light (which I like too)--but the turn signals tend to be rather narrow and the lights overall are generally underpowered affairs. There are some LED ones out there, and they might be a good starting point for something to modify however.
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