Nice! I guess the rss link changed in the last 8 or so years
Though the old one still seems to work.
The problem with groupme is that the messages are often delayed, sometimes even hours late.
A better solution might be rss to email, and then have gmail forward the email from your gv # to your cell # (you can get the number for this by going to voice.google.com and sending a message to your phone, and then replying. You'll see the 'email address' it creates for you to send messages to your cell #).