I believe it's on a permanent live, so leave it long enough and it will drain the battery.
Bummer, are there any which do turn off?
I couldn't say for sure and can only go off of the couple I've tried, I think they're designed that way.
In my very limited experience, when I kill the ignition the bluetooth/wifi connection doesn't drop, so can only assume that's because it's still hot. I'm guess someone with some electrical brains could fit an inline switch for the OBD2 port, so you could manually turn it off without disconnecting the device but I don't think I've seen it done on here.
Any reason why you want to leave it in all the time, mine fits nicely into the ashtray/coin holder when out of use.
That's a shame, it can't be that hard to make something that turns off or goes to stand by when the engine is off?The reason I want to leave it in all the time is just pure laziness, I would have thought that technology can worry about whether the adapter is sending a signal or not so I don't have to.
I looked into this last night and it seems that Stu's right, it's always live, but there's many people that leave the OBD reader plugged in(on other makes) - some over a couple of years or so, with no negative effect.
Try it for a week - I reckon you'll be ok.