Here a way to send sms from computers no deed a cable or wifi or anything to connect your phone to the computer.
After you send an sms via "Email to Text", you can find the message in your email's sent box, all you need to do is to directly reply the message, then your message will be sent to the same recipient again as an sms message.
Check this out
Gmail and yahoo mail is tested works well.
Enjoy the day.