Made a generic sms sender, for check_mk monitoring + sending password of accounts.
You can send sms by filling in a form, or using a url like:

http://smsgateway.local:8080/sms/0612341234/Message%20met%20spaties

It uses a Raspberry and a sim800L module.

Remove pin from simcard fix:

sudo minicom -b 115000 -o -D /dev/serial0

 AT+CPIN?
+CPIN: SIM PIN

AT+CPIN=0000
OK

AT+CLCK=”SC”,0,”0000″
OK

AT+CPIN?
+CPIN: READY 

Cron

@reboot sh /home/pi/launcher.sh 

Launcher

cat /home/pi/launcher.sh
#!/bin/bash
cd /home/pi
while true; do
/usr/bin/python newapi.py
done

newapi.py (uses flask)

import serial
import RPi.GPIO as GPIO     
import os, time
import sys

from flask import Flask, render_template, request
app = Flask(__name__)

from flask_wtf import FlaskForm
from wtforms import StringField, PasswordField, BooleanField, SubmitField, TextAreaField
from wtforms.validators import DataRequired

from flask import render_template

app.config['SECRET_KEY'] = 'you-will-never-guess'

class FormForm(FlaskForm):
    telnumber = StringField('telnumber', validators=[DataRequired()])
    messagepart = TextAreaField('Text', render_kw={"rows": 5, "cols": 20})
    submit = SubmitField('Send Sms')
 
@app.route("/sms/<number>/<message>")
def action(number, message):
        num = number.encode() 
        mes = message.encode() 
	GPIO.setmode(GPIO.BOARD)   
	# Enable Serial Communication
	port = serial.Serial("/dev/serial0", baudrate=9600, timeout=1)

	# Transmitting AT Commands to the Modem
	# '\r\n' indicates the Enter key
	port.write('AT'+'\r\n')
	rcv = port.read(10)
	print rcv
	time.sleep(1)
	#port.write('ATE0'+'\r\n')      # Disable the Echo
	#rcv = port.read(10)
	#print rcv
	#time.sleep(1)
	port.write('AT+CMGF=1'+'\r\n')  # Select Message format as Text mode
	rcv = port.read(10)
	print rcv
	time.sleep(1)
	port.write('AT+CNMI=2,1,0,0,0'+'\r\n')   # New SMS Message Indications
	rcv = port.read(10)
	print rcv
	time.sleep(1)
	port.write('AT+CSCS="GSM"'+'\r\n')   
	rcv = port.read(10)
	print rcv
	time.sleep(1)
	# Sending a message to a particular Number
	port.write('AT+CMGS="'+num+'"\r\n')
	rcv = port.read(10)
	print rcv
	time.sleep(1)
	port.write(mes+'\r\n')  # Message
	rcv = port.read(10)
	print rcv
	port.write("\x1A") # Enable to send SMS
	for i in range(10):
	    rcv = port.read(10)
	    print rcv
        return 'OK'
@app.route("/form")
def form():
    form = FormForm()
    return render_template('web.html', title='Web Sms', form=form)
@app.route('/data', methods = ['POST', 'GET'])
def data():
    if request.method == 'GET':
        return "The URL /data is accessed directly. Try going to '/form' to submit form"
    if request.method == 'POST':
  
        telnumber = request.form['telnumber']
        messagepart = request.form['messagepart']
        num = telnumber.encode() 
        mes = messagepart.encode()
	GPIO.setmode(GPIO.BOARD)   
	# Enable Serial Communication
	port = serial.Serial("/dev/serial0", baudrate=9600, timeout=1)
	# Transmitting AT Commands to the Modem
	# '\r\n' indicates the Enter key
	port.write('AT'+'\r\n')
	rcv = port.read(10)
	print rcv
	time.sleep(1)
	#port.write('ATE0'+'\r\n')      # Disable the Echo
	#rcv = port.read(10)
	#print rcv
	#time.sleep(1)
	port.write('AT+CMGF=1'+'\r\n')  # Select Message format as Text mode
	rcv = port.read(10)
	print rcv
	time.sleep(1)
	port.write('AT+CNMI=2,1,0,0,0'+'\r\n')   # New SMS Message Indications
	rcv = port.read(10)
	print rcv
	time.sleep(1)
	port.write('AT+CSCS="GSM"'+'\r\n')   
	rcv = port.read(10)
	print rcv
	time.sleep(1)
	# Sending a message to a particular Number
	port.write('AT+CMGS="'+num+'"\r\n')
	rcv = port.read(10)
	print rcv
	time.sleep(1)
	port.write(mes+'\r\n')  # Message
	rcv = port.read(10)
	print rcv
	port.write("\x1A") # Enable to send SMS
	for i in range(10):
	    rcv = port.read(10)
	    print rcv
       
        return '<a href="/form">Nog een SMS sturen</a>'
@app.route("/checkmk")
def checkmk():
        # Enable Serial Communication
        port = serial.Serial("/dev/serial0", baudrate=9600, timeout=1)
   
        port.write('AT'+'\r\n')
        rcv1 = port.read(30)
        time.sleep(1)

        port.write('AT+CPAS'+'\r\n')
        rcv2 = port.read(30)        
        time.sleep(1)
    
        port.write('AT+CGREG?'+'\r\n')
        rcv3 = port.read(30)
        time.sleep(1)
    
        port.write('AT+CGATT?'+'\r\n')
        rcv4 = port.read(30)
        time.sleep(1)
    
        port.write('AT+CSQ'+'\r\n')
        rcv5 = port.read(30)
        time.sleep(1)

        return 'OK of niet' + rcv1 + rcv2 + rcv3 + rcv4 + rcv5
if __name__ == "__main__":
   app.run(host='0.0.0.0', port=8080, debug=True)