If you use Krill lights, remember they are just markers. You get enough light to navigate in a dark room, during an electricity outage. Or you can read a book, if you hold the light very close.
That's about it. Not an emergency beacon, for sure !

+ do not keep them with the batteries inside them. I recently discovered that many of my Krill lights (in my car kit) are unusable, because the weight of the batteries inside the tube, alongside with travel vibrations, distorded the spring, so that the electrical contact is no longer good....

If you need something specifically for signalling, there are small (and light) flashers, like these ones, for instance: pelican mini flasher . Get three.