Thanks girls

Nic - Kelly has an article on SWI here.
They are four injections of 0.1ml sterile water into the back, just under the skin. It aims at essentially confusing the pain sensors. They can be done in a line of four or in a square generally around the sacral region, and they are described as 'wasp stings'. They're supposed to be great for back labours but i agree with the article where it says needing to be 8-10 on the pain scale for them to be effective/worth it as they really did sting like a b**ch!