The receive part I used was a cell phone and not land line one, so I do not have experience with that.
If you want to do it with cell phones, then check out some GSM phones and their developer manuals (Most Nokia and Erricson phones will do just fine). However, if you are going to use cell phones, then check out the SMS (short message system) which you send a text message or email to the receipient which your system can retrieve it and do something. The cost is much cheaper because you can buy SMS devices / services. Search on the internet for SMS technology or just go to www.gsm.org . Joe
