Since we are headed back into the James Bond film season, today’s invention is, I hope, worthy of Q.
The spokes of a motorcycle or bicycle wheel could each have a crossbow bolt attached, so that the sharp ends point radially outward.
A signal from the intrepid, double-0-licensed rider would cause these bolts to be released at the right moment and flung from the wheels (backwards from the rear one or forwards from the front one).
An approaching assailant would be at least distracted by these, if not actually skewered.