Hi,
You are right that there are some expensive third party applications out the there, but they can normally do more than just sending a single message to a single phone. That being said, I had to write my own application (about 16 hours spent on the development) to do some tests around a specific problem I had at a customer site. Believe me, it's not rocket science, it's a plain and simple text based protocol being used. The SDK from spectralink is easy to follow and it is very easy for a skilled "programmer" to make a simple program using IP to send messages via the OAI gateway. If you connect via procomm or another terminal program to the RS232 port you can even "if you interpret the SDK right" easily send the commands necessary to send messages.
I2007