Get this if phone calls are important to you
This is very loud and I can hear it even when a lot of machines are running in my shop.  The reason it only gets 4 stars is because, even though my cell phone is set with ring & vibrate (the vibration is what makes it work, I think), it doesn't go off every single time.  Don't know why, maybe I haven't set it up correctly?  But it does work most of the time and is pretty hard to miss.
Rating: 4 stars