SMS for login to website
You Can go for Twilio Module

The Twilio module provides integration with the Twilio cloud communication platform 
allowing for your Drupal site to integration Voice and SMS functionality.


What you can do using this module 

Ability to store and access TwiML
Rules event to act on incoming SMS message
Rules action to send an SMS message
Rules event to execute TwiML scripts
Hook for incoming SMS messages
Hook for incoming voice calls
User object phone number storage and validation
Uses libraries api to manage the Twilio php library
Support for international texting
Support for MMS