When installing life safety devices try to install your notification device near the sleeping area. This will help wake the occupants during a fire or carbon alram. Please see below for 4 wire smoke installation.
The purpose for the wifi extender on ADT Pulse is to increase the reliability and communications with none Z Wave devices. The wifi extender works for wireless cameras and tablets. If you want to increase communications with a Z Wave device create a bridge by using a lamp module as a repeater.