I found it in a tweet and I was pretty sure it was photoshopped silliness but people were acting as though it was a real thing. I had to google to confirm what's what...
Teenage Engineering's tiny handheld TX-6 mixer offers an instrument tuner | Engadget
It also has built-in synth and sequencer capabilities.
I think because it's like 4" across and anyone who would buy one of these probably has all the functions memorized.