~$ gsmsendsms -h gsmsendsms: [-b baudrate][-c concatenatedID][-C sca][-d device][-h][-I init string] [-t][-v][-X] phonenumber [text]

  -b, --baudrate    baudrate to use for device (default: 38400)
  -c, --concatenate ID for concatenated SMS messages
  -C, --sca         SMS service centre address
  -d, --device      sets the destination device to connect to
  -h, --help        prints this message
  -I, --init        device AT init sequence
  -r, --requeststat request SMS status report
  -t, --test        convert text to GSM alphabet and vice
                    versa, no SMS message is sent
  -v, --version     prints version and exits
  -X, --xonxoff     switch on software handshake

  phonenumber       recipient's phone number
  text              optional text of the SMS message
                    if omitted: read from stdin

(it's in the gsm-utils package)