Gammu is a cellular manager for mobile phones/modems. It contains libraries and functions for ringtones,logos,phonebook,SMS,etc. (used by external software), a command line version (with backup/restore) and SMS gateway (with MySQL and PostgreSQL supp
Gammu smsd is now the main tool for SMS payment in my local currency software Cclite [here on sourceforge, shameless plug!]. Very pleased with it, and it's improved continuously over the past few years. Currently testing with Raspberry Pi. Thanks folks!