This place has a mind bending array of sensors and devices for home security.]
]http://www.x10.com/promotions/sc1200_149_mega_home_security_system.html?EM
It does work. I had one from them for my parents.
Heart of the system is a phone dialer. When it is tripped, it dials up to 6 numbers in a row, using regular land lines, until someone (human, not answering machine) picks up. Then, it plays a recording which you put on the dialer letting the person know the message you want them to hear. Then, it is that person's responsibility to figure out what to do next.
Simplest version is to use the keychain pendant PANIC button...this starts the dialing process.
System can be tripped by many, many devices, but you don't have to use them all. It can be a burglar alarm, turn lights on and off, all sorts of things.
You purchase the system for around $150, current sale price, then there are no other costs.
The last number you leave on the dialer can be 911 in case nobody else answers the call. This forces 911 to dispatch someone to the house, assuming you provide the address in your message. This is actually all the PAID SERVICES do...when alerted, they call the house back and unless a person answers indicating a false alarm, they call 911 for you.