Since each list in RTM has its own feed, you can easily trigger all kinds of actions using the (free) IFTTT (http://ifttt.com) service.
Here's an example that I use for being notified by SMS when my wife adds an item to our "need to talk about this" list.
1. Create Recipe
2. Pick "Feed" as the Trigger.
3. Choose "New feed item"
4. Paste in the Atom feed URL of your list
5. As Action choose "SMS"
Voila! You'll now get an SMS each time an item is added to a specific list.
Note there are a bazillion different action channels you could pick from instead of SMS, for example auto-creating a Google Calendar appointment, switching on a WeMo light switch, tweeting something, etc...
Imagine for example using a smart list with postponed items, and then auto-tweeting "I'm ashamed, I just postponed a task for the 10th time in Remember The Milk." :)
(disclaimer: not affiliated with IFTTT, just thought this might be helpful)
Posted at 12:23pm on July 31, 2013