Automatically switch bluetooth headset to default sound device when turned on

I have a set of Bluetooth speakers that I use randomly. The majority of the time, I just use the builtin speakers on my MBA with Mountain Lion. But there are times when I want to use my Bluetooth headphones. Unfortunately, everytime, I have to go to Bluetooth, the device, and then set it as an audio device. Is there anyway to do this so when I turn on the BT headphones, it connects automatically and makes it the sound device?