You do have to power it on with a button but then it automatically connects with the last used BT device. I fixed a 3.5mm jack plug behind another device on the dash with just the pin sticking out, this then holds the adapter mechanically as well as connecting it to the empeg's aux so it looks quite tidy and you can get to its AVCRP buttons.

I also wanted an autoconnecting one and the most likely candidate was at least twice as much and was still not guarenteed to work as I suspected so this is good cheap compromise and is removeable for other uses.