I don't suppose "safety" is something that can just be purchased, but I think there are some accessories that contribute to visibility and address some of the needs to be safe, like lights and reflectors and helmets.
Safety, to the degree we have influence over it, is probably most affected by our behavior and to a lesser degree by gadgets we buy and use. I was studying the guidance on this site:
https://bicyclesafe.com/ and read the following under #10: "A car runs into you from behind. This is what many cyclists fear the most, but it's actually not very common, comprising only 3.8% of collisions."
I live in a rural area and rarely cycle in urban areas and busy intersections are not my greatest concern. I have to this point, mostly been concerned with being struck by a motor vehicle that doesn't give me sufficient room when passing, most probably because there is opposing traffic -- the "scissors." The greatest portion of my riding is on undivided two-lane highways where motor vehicles are going 50 mph or more. Sometimes there is a shoulder, and often not much. There are also often poor sight lines in the mountains with hills and curves.
Because of this, I've focused mostly on making myself and bike more visible from the rear. I have flashing taillights and a reflective triangle for example. I think to a certain degree, this is meaningful in as much as it helps me be seen when I'm in the shadow of trees. On the other hand, it's probably naïve to think this will increase my safety with drivers who do see me but are willing to try to squeeze past too close anyway. I do have a mirror so I can see cars approaching from behind. If I have a wide shoulder, I can move FRAP, but if I don't have sufficient space, I don't want to invite the driver to pass. Sometimes the speed differential is too much to think that they won't pass. If I see cars coming the other way and I know I'm going to get scissored by a car coming up behind me 60mph faster than me, I'll get off the road. My mirror is essential to seeing cars coming from behind. In heavier traffic with a very narrow space, turning my neck risks the bike wandering.
So far I've got:
a rearview mirror on the left
a flashing red light on the back
a reflective triangle on the back
The "Door Prize" is a big concern for me lately. I'm riding around a lake -- it's a 150 mile ride -- and there are places where hundreds of cars (miles long) parallel park on the shoulder for access to the beach. Those cars put me out in the lane with traffic going 50 mph. The speed differential makes me want to ride FRAP, but getting doored could push me under the wheels of a passing truck. I really don't expect the beach-goers are going to look before they open their door, so I'm skeptical that a headlight would help me be seen better in this case.
Preventing collision types #1, #3, and #8 (
https://bicyclesafe.com/) can be aided with a headlight. I have and use a flashing white visibility light on the front. It's one of these cheap jobs that are sold under various brand names:
It's not bright enough to see by at night, but I think it adds some visibility in the day. I also have a 1600 lumen Fenix PD36R. This is my EDC flashlight. I can mount it on my bars with a bar-mount. It will only run at 1600 lumens for 3 hours, but at 350 lumens it will run 8.5 hours. I'm thinking I should use it since I have it anyway. I don't generally ride at night.
So what gadgets am I missing? Flag? Orange vest? Pinnacle Technologies Traffic Annihilator
™ ?