I have no clue what "google desktop gadgets" are, but you might have a look at the source code to see how it dispatches SMS to the provider. Maybe there is a API.

You could try to contact the autor of this gadget and ask if he used a API or scraped the website if the src-code is not available.

Yes, be sure to download the lates version before you start to modify anything :-)

Cheers
Bjoern