After reading much about DRL installation, I've done it to my 2011 SL, too.
In a nutshell, I've tapped into the 57 wire, ran wires inside the cabin via the grommet behind the glove box, and incorporated a switch to turn on and off the LED fog lights. I've wired it so that the switch's blue light illuminates when the LEDs are on, and when I push the button to turn it off, the blue light also turns off.
H11 LED bulbs from SuperBrightLights.com:
https://www.superbrightleds.com/moreinf ... mens/1278/
On/Off switch inside the cabin:
https://www.amazon.com/dp/B01IT0VDLW/re ... XDbY73BA7T
My wiring diagram:
I'd be happy to answer any questions. :0) Thanks everyone!