Remember that crazy small, RF receiver used with Logitech's VX Nano
? Meet the Bluetooth 2.0+EDR equiv, the Princeton's PTM-UBT3S which measures just 19-mm (0.75-inches) long. So yeah, it's small, in fact, it's claimed to be the smallest available in Japan when it ships in September. Whether or not it's the world's smallest is irrelevant as it's surely suitable for full-time laptop or handheld bunging without concern for sheering it off. Yours for ¥2,480 or $21 beans.