Put the chilli oil, lime juice, honey and salt in a non-metallic bowl and stir until the honey has dissolved. Slit the prawns along their backs and pull out the black vein, then toss in the marinade, pushing it into the shells. Leave to marinate for 10 minutes.
Thread the prawns onto 4 metal skewers and cook over a barbecue or under a preheated grill for 2–3 minutes on each side until they turn pink and are cooked through. Serve immediately with lime wedges to squeeze over.