I have a bluetooth headset I like. I use it at night sitting on the sofa messing around on my laptop to listen to music or videos on YouTube. However one annoyance I have always had with them is that when I connect to them they would launch iTunes.
So I googled around a bit and noticed that there was an app called iTunesHelper that was part of my Login Items. I removed it from there, and that seemed to do the trick, at first.
After a few weeks I noticed the behavior came back. I was perplexed, until I realized iTunes must be restarting the helper when it was used. After a 2 second test I realized this was true. So I helped the helper.
# cd /Applications/iTunes.app/Contents/MacOS/
# sudo mv iTunesHelper.app iTunesHelper-shutup.app
# sudo pkill iTunesHelper