We recently pushed live a new feature (alpha) on task.fm that allows you to setup reminders via a SMS (text message).
How it Works:
Just send a message to: (773) 273-9947 with your reminder. Remember Task.fm understands natural language, so write the message as if you were talking to your assistant. For example:
remind me to pick up the dry cleaning in 3 hours
Note: This is a pro feature for upgraded members of Task.fm and currently only supported in the U.S (we will role out to more countries soon). To upgrade visit this page.
Also, remember this is an Alpha or experimental feature – so you may experience some bugs.  If you do please let us know.
What do you think of the new feature?
