arduino project

My project is to use an arduino circuit like ATMEGA328P Pro Mini 328 Mini and a SIM 800L gprs GSM circuit board, prefered board to be smallest possible or ( if you can recommend better module for this project is fine let me know) conected to a the main alarm control panel and whenever there is an alarm this module call and send a text massage to the customers mobile number. So you need to write a program for the arduino to register the customer mobile number upto 5 numbers through sms ( numbered entered by sending text to the arduino) And also by sending a text massage customer can check the numberes which added and can delete them if want to. And by a receiving a text massage can get the sim card signal strengh and information if enquired. The arduino is activated by recieving negative 12v supply on one of its input. (Alarm activated) Another input should show the status of the alarm of it is set or unset.( negative applied is SET or negative removed is UNSET) send a text massage for each state. One of the arduino output is switched on and off by sending a text masage (pulsed) This is the basic purpose of the projects which the board is supplied from the 12v alarm supply so a small power circuit i needed to lower the voltage and supply the arduino. Please let me know if you are able to program and design the circuit for this purpose i may need one or two more function from the arduino input,output controlled by sms. Looking forward to hear from you. Thanks