I see the benefits of this as:
* Reply to / send new SMS’s to any of your contact list via any of the four methods (e-mail / GTalk / Chrome extension / web-app).
* Quick replies without having to touch your phone, convenient if you’re at work or if you prefer typing on a keyboard.
* Can easily SMS large number of people.
* If you don’t have access to your phone (ie. left it at home) you can still read / reply SMS’s.
Requires substantial permissions, but from a reputable developer. Direct market Link: https://market.android.com/details?id=com.koushikdutta.desktopsms