SMS etc

Hello all, I apologize if this is deemed off topic, but I think there is enough content to warrant the question. Some time ago there was a lively discussion about SMS paging and the providers for that in relation to emergency operations NMS paging etc. Who can point me in the direction of the still serving providers and maybe give some color commentary on the SMS to SMTP or other paging methods many of you use to provide the paging of engineers? Please reply off list and if there is any interest I will summerize back to the list. Thanks, Jim