I have had a few flat batteries recently, mostly when it has rained a lot. When raining the battery lasts two days parked max.
I also fitted a bluetooth streamer last year..
http://forum.a8parts.co.uk/showthread.php?t=15284
which has permanent 12v but shuts down when it receives MOST shutdown command and wakes up when MOST wake command is received.
What has become apparent is that the car is waking up and going to sleep all day long when parked. When I turn the car off and lock it, the bluetooth disconnects, when I unlock the car it connects and MAPS app gives suggestion of where to go. What I find when it rains is while I am sitting in the house or at work the phone keeps alerting how many minutes to work/home and how the traffic is and keeps reconnecting to bluetooth. The MOST bus is probably repeatedly waking everything up and booting the MMI.
This is definately not bluetooth going in and out of signal range. I believe it is the proximity sensors on the underside of the door handles being triggered by rain.
Attachment 22967