If you were mailing the cables to random people, you wouldn't use wifi, it's true. You'd just want the fake keyboard to just use a terminal to download and install a trojan.
If you can fire off a successful "curl | bash" on an internet-connected machine, wireless isn't needed.
Of course, without wifi you've only got a USB Rubber Ducky clone [1] whereas with wifi, you've got an NSA COTTONMOUTH clone [2] which I imagine is much more likely to get your talk accepted at DEFCON :)
Opening up a terminal while the user is actively using their computer is going to be a huge red flag and give the whole game away. Presumably with a local attack, the attacker will wait until the user is distracted or away from their computer before taking control.
If you can fire off a successful "curl | bash" on an internet-connected machine, wireless isn't needed.
Of course, without wifi you've only got a USB Rubber Ducky clone [1] whereas with wifi, you've got an NSA COTTONMOUTH clone [2] which I imagine is much more likely to get your talk accepted at DEFCON :)
[1] https://shop.hak5.org/collections/physical-access/products/u... [2] https://en.wikipedia.org/wiki/NSA_ANT_catalog