Cheap way of remote diallling but is still flawed in a break in situation. I.e if the signal was bad and the call attempt failed. Plus the whole point of a system monitored by a central staion using for example BT redcare, is that A: alarm activation AND the line connnection is monitored, and that B: central station will be able to get you a priority police response.
Would be a good addition to a Redcare landline as a back-up GSM line though.