Teacher and blogger Vicki Davis highly recommends Celly for parent/teacher communication.
Here’s what she writes (followed by the video):
I love this app. Here’s the video about how you set up a parent “cell” so you can communicate with them via cell phone WITHOUT giving all of them your cell phone number! LOVE IT! Awesome.
I’m adding it to A Beginning List Of The Best Resources On Using Technology To Help Engage Parents.