It was a really big deal when they became mass market (90s, I think?) and were the peak of “cool” at the time. But they’re absolutely horrible for energy consumption.
There was a Japan-only Game Boy Light that was the form factor of the Game Boy Pocket but with an electroluminescent display. I have one, and to this day it's one of my favorite handhelds. It males grayscale games are absolutely gorgeous in the dark.
Surprisingly, it has a very decent battery life - 20 hours without the backlight, 12 with.
Casio comes to mind when coming up with EL devices for example. The classic G-shock I have on my wrist right now touts a "Electro Luminescent Backlight", though I rarely use the light.
Here’s an example: https://upload.wikimedia.org/wikipedia/commons/b/b8/66Charge...
They compete mainly with the fixed-segment monochrome LCD display market. I’ve seen some in multicolor as well.