Since he refuses to say what it actually was, it's apparently the aeroband aeroguitar. If you see "I found the worst guitar product ever" or "THIS IS NOT A GUITAR" in the recommended videos to the side, they're talking about the same thing. Really any videos from the past couple of weeks with a matte black guitar in the thumbnail that looks like the strings on the fret and the strings on the body are separated by a weird block, they're probably about this.

It's basically a low-quality midi-controller with a few guitar synthesizer presets that plays notes when the string segments on the body are hit. It does not have strings on the frets, just string-shaped buttons. It sounds horrible, is apparently extremely buggy with its sensors just constantly malfunctioning, and it costs almost $500.