Help needed

I'm even ashamed to write this, but here goes. When we lived in France the dogs slept in the study right next to our bedroom. Like me, they were rarely allowed in the bedroom, but that's another story.
Here in the UK they sleep in the garage which is a relatively short distance vertically from where we sleep now. The other day Max was suffering with the squits and attempted to let himself out of the house in the middle of the night. It was only by chance that we heard him, so I got up, opened the door and let him out.
All this just fed Jan's ongoing paranoia about not being able to hear the dogs in the middle of the night.
So what did she send me out to buy yesterday?
A baby alarm.
One that can be set up in our bedroom and also near the exit door that the dogs would use to leave the house, so that we could hear them.
When you meet her, Jan comes over as nice and normal but, mes braves, I keep a diary. A diary that might be needed sometime in the future and that  sure as hell I will use in my defence.
Talking about needing help (that's a good segue - Ed), do any of you super smart people out there know what the above tree is?
I know one of you is very clever but I can't remember which one. Our Ladybird book of trees and shrubs didn't help, nor did at least five exhausting minutes searching the internet. Gissa clue.