The price for such a service varies considerably depending on the area where you are located. I can tell you that the ones that have their own security people who respond are quite expensive and only available in restricted areas. Because of the time required to respond. They only cover areas where they have multiple customers to justify the cost of the manpower and minimize the response time. If you live in a rural area, forget it, the service will not be available. The best thing to do is call around to some of the major security companies in your area and ask them the question.
I've learned that there is a fine line between genius and insanity