if anyone's curious: that's a ps4 controller with a gold buttons mod from eXtremeRate and a usb-c mod from Casual Coders on Tindie, along with some ps4 controller cell phone mount from amazon.
I use a 6-inch usb-c cable to connect the controller to my phone, and it registers with Retroarch Android, which is running a simulation of VirtualBoy Bowling. In the emulator settings you can enable red/blue anaglyph mode, which works with these paper 3D glasses.