From the author...
Studley, sadly a demonstration of my lamentable habit of going over word count!
Once you have synced your contacts with DeskSMS you can trigger your phone to call a number from the browser. I couldn't convince myself this was a key feature so I dropped the paragraph. If you have your phone rigged to some sort of hands free device on your desk it could be of use.
@ AC - it's free at the moment. It moves from a free beta to a paid app at the weekend. There may be a yearly or an all-time fee offered. As I understand it the developer hasn't decided on that yet but as you say $4.99pa seems most likely.