/usr/bin/gsmsmsrequeue is in gsm-utils 1.10+20120414.gita5e5ae9a-0.3build1.
This file is owned by root:root, with mode 0o755.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48  | #! /bin/bash
#
# /usr/bin/gsmsmsrequeue: Re-queues failed SMS
#
# written by Matthias Goebl <matthias@goebl.net>
SPOOLDIR=/var/spool/sms
PRIORITIES=3
SMSADMIN=root
SUBJECT="SMS delivery report:"
send_notify()
{
  tmpfile="$SPOOLDIR/tmp/"`basename "$1"`
  status="$2"
  if mv "$1" "$tmpfile" 2>/dev/null; then
    # extract the first tab-separated field after the phone number as
    # email-address to send the notification to
    mailto=` cat "$tmpfile" | sed -ne '1s/^[^	]*	\([^	]*\).*/\1/p' `
    test -z "$mailto" && mailto="$SMSADMIN"
    cat "$tmpfile" | mail -s "$SUBJECT $status" "$mailto"
    rm "$tmpfile"
  fi
}
do_accounting()
{
  true;
}
test -r /etc/default/gsm-utils && . /etc/default/gsm-utils
for p in `seq 1 $PRIORITIES`; do
  ls "$SPOOLDIR/failed$p" | while read file; do
    if expr "$file" : ".*rrrrrrrrrrrr" >/dev/null; then
      send_notify "$SPOOLDIR/failed$p/$file" "failed"
    else
      # re-queue SMS
      mv "$SPOOLDIR/failed$p/$file" "$SPOOLDIR/queue$p/${file}r" 2>/dev/null
    fi
  done
done
for p in `seq 1 $PRIORITIES`; do
  ls "$SPOOLDIR/sent$p" | while read file; do
    do_accounting "$SPOOLDIR/sent$p/$file" "sent"
    send_notify "$SPOOLDIR/sent$p/$file" "sent"
  done
done
 |