Why insisting on the wireless part ? Again, wireless pairing on arbitrary devices is not easy.

Your options :

NFC : cool, how many desktop computers support NFC ? how many smartphones support NFC right now ? And do you really want to keep both devices glued to each other while the transaction is performed ?
Wifi : ok, how do you enter the passphrase, how do you retrieve the device IP, how many desktop computers use Wifi too ?
Bluetooth : pairing is not trivial either.
Zigbee : not deployed.

USB : connect, no setup, done. If you get a device and a USB cable, I figure people will know what to do with it