I'm not a fan of the turn signals on motorcycles because of how easy it is to forget that they're on. Sure, you can get into the habit of pressing in to cancel the signal at random times, but that's just something that distracts from the ride. So I made a simple circuit to add vibrational feedback that vibrates with the blinking of the lights on my Zero DS.
The schematic for this is pretty straightforward, the output for both signal lights gets brought in to a voltage regulator to bring the voltage down from 12v to the 3.3v that the vibrator is rated for. The purpose of the diodes is to prevent the signal from one channel looping back to the lights for the other side (otherwise both sides would light up regardless of the way you signaled).
I threw together a proof of concept with parts that were already on hand and had good success with it once I added some capacitors to the inputs and outputs (needed for this particular regulator, not shown in the schematic or the photos).
I was a bit worried that there wouldn't be a ground return line brought out to the switch cluster, but fortunately one is used on the horn switch (gray wire on mine). The location I hot glued the circuit to turned out to not be ideal because it shares that space with the wire bundle, making it difficult to close everything back up without the turn signal lever rubbing on the top half of the cluster.
Here you can see where I attached the vibrator to the sidewall of the case. I think that this is also a better location to stuff the circuit.
Test video with it plugged in to the bike before I mounted it to the handlebar:https://youtu.be/yRY1YhNtwUw
While this setup works and is effective while the bike is stopped, it is very hard to notice if the bike is going faster than 5-10mph. I intend to make a small circuit board that people can buy as a kit, and will try out a few different parts for making the vibration, maybe something that takes the resonant frequency of the handlebars into account. I'm also thinking of making a clamp on unit that can go on any bike easily and could have a much bigger motor, but haven't come up with a clean way to splice that into a wiring harness. I also have a feeling that this system will work best on electric bikes since they don't have an engine shaking the entire bike.