Texty is a beta app that allows you to send SMS from your computer by routing it through your phone as if you are remote-controlling it. The phone will need to be online of course, WiFi or 3G, and you need to have the proper plug-in installed (Chrome plug-in available).
It works, but PDA*Net, the free version, will do this with a USB cord. If you are near a computer, you are near power. Why is your smartphone NOT attached to the PC for power? Hmmm...
Still, it is worth a try if you can get into the beta.