SMS Reminders for Course Signup module I am using Drupal 7 version of Signup module. It send email reminders before the course starts X number of days. Is it possible to send SMS reminders using another module. If not then where i should be looking in the code ?

thanks
You can use any sms integration api. I personally like Twilio. 

There is a module for twilio integration as well: link

You will need to find a place from where the email has been sent, it would be in the code or possibly through Rule module, in either case you need to add a line of code which should utilize twilio api and send sms to the destined users.