eSMSd is a simple daemon for connecting a Gnokii-handled mobile phone with SQL database into a SMS gateway. It bears great simplicity, and is therefore suitable for custom projects and smaller businesses, but is still powerful enough to handle larger loads. The project is intended as a replacement for Gnokii's SMSd, but is much simpler (therefore great for hacking, learning, and SMS magic) and also a little more portable (SMSd tends to crash on AMD-64).
SD SMS Master is an SMS-sending server. The Web server (master) contains the SMS Master itself. Clients (users) connect to the master and create orders. Orders contain a text to send and a list of numbers to send to. The master then connects to remote machines (slaves) and distributes the order numbers (+text) to all enabled phones on the slaves. The communication is one-way; incoming SMSes are not read.