This  Notice Board is quite smart. It is a re-purposed  unused old LCD monitor. The messages to be displayed on the notice board ( an old LCD monitor) can be sent from any mobile phone. The user should also provide an authentication code for the message to be displayed. The video below shows it.

                                          The system consists of a  SIM900 GSM modem, and two avr microcontrollers. The VGA signal generation

is done using an Atmega16, The AVR bit-bangs  VGA signals through its SPI port. I modified the AVR VGA/PAL Terminal example by Vassilis Serasidis to drive the VGA monitor. Since the code running on the Atmega16 was critically timed so that not  much more functions could be handled by it without interrupting the VGA out. So I choose another microcontroller, an Atmega8 ( a AtTiny  would be enough, but I had a spare Atmega8 with me) to handle the GSM message part. The entire circuit is shown below:

The Atmega8 configures the GSM modem, receives messages, and after authentication, sends it to the display controller built around Atmega16 through a software serial port (pin4). The GSM modem is interfaced through the standard AT commands. The hardware UART of Atmega8 is used to send the received message after formatting to display to the display controller. The GSM modem is based on the popular SIM900 architecture and was bought from rhydolabz. It has TTL outputs (5v &3.3V) so that no level converters are needed in between the GSM module and microcontroller.
All the codes are available in my github.