This device is called a Sensaphone 1000 from Phonetics, Inc., my specific unit was rebranded as a Best Power Technology but it is a Sensaphone 1000. It a rather old device from the 1980's but it still works great.
This is a Desktop Environmental Monitoring System. It designed to monitor homes or business, I use it to monitor the tank room when I'm away on vacation or business trips.
It provides two-way communications (it can call me, and I can call it) over the phone line. It has voice synthesizer to talk about power status, temperature, ambient noise levels (it can hear fire alarms). It even has a microphone so I can hear what's going on in the room.
I can be directly wired for three switches which can be used to monitor windows or doors being opened or can be used to detect power outages across multiple circuits such as detected a tripped breaker or blown fuse.
It can be programmed to dial multiple phone numbers encase I can't be reached and can even dial numbers such as pager notifications.
When local reef keepers ask me to watch their tank when away, this is the first thing I bring with me.