Based on one physical address, this service alerts for tornado, severe thunderstorm and flash flood warnings (email/text only). It allows up to three phone numbers (with associated text messaging if mobile) and an additional three email or text messaging contacts. All of this for $9.95 a year.
This service is for one smart phone as it uses the phone's geo location service. When launched you have the option to be alerted on tornado, severe thunderstorm, flash flood and lightning (with an all clear). The three levels of service are NWS (National Weather Service alerts only), Lightning alerts only or a bundle of both.