I could never figure out what the purpose of the trunk button was. It doesn't open the trunk - just release it. When you open it from the back, the release button is on the handle anyway.

 

I've been wondering what that button was for months since I got the car. Why would the alarm go off on a hill?

 

The button for the hill is to allow the alarm to be set in a mode so if someone tries to pinch the vehicle by simply towing it the alarm will be activated, I presume these are USA vehicles as they normally have the highest state of security systems.

 

The button with the "sound" looking picture on it is for the motion sensor inside the car as cbher stated. It is mainly for convertables, but also works when you leave the windows down.