smsX is an application (and web client) that allows you to send text messages. We use ClockworkSMS to send the messages so you will need an API key and clockwork credit.
The application is free to download for Windows!! (its it reccomended that you have Windows 7 or above.
There is a web client if you would prefer that. 
THE WINDOWS APP IS NO LONGER UNDER CONSTRUCTION - there will be no more updates. Don't worry smsX will still exist! But we are going to make it all web based! Yes! A web application free for all to use