You could also hitch up an analog modem to a POTS line, and then let your paging software dial your cell/home number. You won't hear anything, but the CallerID will let you know that your monitoring system is *desperately* trying to get in touch :-)
You could take it one step further and get an FXO card and put it in a very basic asterisk server. Write a simple program which call be pinged with issue reports as an argument, then pass those arguments to festvox or other TTS application. Output to WAV, convert to GSM, generate an asterisk call file (or write an extension) that calls you on the analog line, and plays you the sound file. I've done this at several employers. It works fairly well - perhaps better than it sounds. If you can get a SIP upstream that will let you set your CID, then send the calls out that route first, and the POTS line becomes a backup - then if you ever get calls from the POTS DID, you know that you have the original problem, plus you know that the connection to the SIP gateway is down. Nathan Eisenberg