Thought I would recommend an ingenious invention...
My lo had a temperature last week and I couldn't seem to get an accurate reading because she was so cranky with the traditional 'stick' type in her mouth that she just got hot and bothered. My mum bought me a little dummy that takes the baby's temperature whilst she sucks. Phew. She didn't mind it at all and luckily we realised her temp wasn't as high as we originally thought. You can just buy them from your normal chemists - called the Kamillosan dummy and comes in a yellow box.