Okay, taking a step back, I’m not quite sure what situation this’d be for. Get stuck in a car, get a flat tire, etc.? Why not just put on the 4-ways?
I don’t carry it in my car anymore, but I used to carry one of those 2×AA bike-taillights, just 3 bright red LEDs inside that you could push a button to select constant-on, blink, pingpong, other patterns. Whole dealy was about as big as a pack of smokes. Ie, go to Bike Planet or whatever, pick up one for 10bux. Neoprene gasket, pry-off / push-on, simple. Came with a belt-clip and I think it also had a fridge-magnet type thingy for sticking to stuff.
Lighting up the area around a flat tire, well, there’s always a… ta daaa!… flashlight, or better yet headlight. Or the wonderful Nitefox UW360 which is made for this kinda thing. I got 2 of ’em.
Got a powerbank? Get one of those 6-LED doodads that just poke into a usb jack. Instant light. Super convenient.
And I just got one of those AA lights that has the slip-on glowy diffuser cap. Hell if I can remember what it was. (Looked it up, Aidler A7 or something. Played with it, pretty nice, does the job.)
And let’s not overlook the 4-ways. Kinda comes with the car…
Okay, if you spin out 3×, bash into a few trees, pinball across the road a few times, and have no lights left intact on the car anymore, sure, you’d need something else. Might as well just carry one of those silly-looking amber blinkylights to stick to the roof of the car.
So… what need is the emergency light supposed to address? I’m just wondering if it’s a solution looking for a problem.