Gmail RSS link will be like this :
https://USERNAME:PASSWORD@gmail.google.com/gmail/feed/atom
But using this link in SMS channel will expose your Password and ID to whole world, so you can use Feedburner service to hide it [Highly recommended] and create your own RSS feed like this
http://feeds.feedburner.com/genothomas
Just put this RSS link into your SMS channel rss feeds and get SMS alert for Emails. Remember to select
Currently this service is available only in India as Google SMS channel is only for india. Many indian carriers supports Google SMS channel like Airtel, Vodafone, Idea etc. so you can enjoy this service of SMS update.
But the only drawback is that if anyone got the link to your Gmail RSS feeds he/she can read your emails directly...!!