hi,
You need to interface GSM with 8051 using UART.
Read the list of AT Commands to be sent for contacts. In response you will get the phonbook details. You need to store that details in array.
To send message, you need to send three things.
1. AT Command
2. hone number stored in array
3. Message
In this way, you can send message to all…!!!
All the best..!!!