Applications built to receive SMS messages can easily be used for instant messaging and Twitter as well. As long as you have user credentials added to your application for the network you want to use (AIM credentials to send a message on the AIM network, MSN for MSN, Yahoo for Yahoo and so on), you can use the exact same application for any network without changing any code. Tropo supports JABBER, AIM, GTALK, MSN, YAHOO and TWITTER for inbound applications.
To add IM credentials, first log in at the Tropo website, then go to "Your Applications" and expand your application so you can make changes to it. Near the bottom of the application you'll see a section labeled "Instant Message Networks" ; click on the symbol for the IM network you want to use, enter in the credentials then click the "Click to Activate" link to the right of the credential boxes.
Note that screen names need to be referenced the same way they're referenced in a standard IM client - this can vary widely from network to network (and even within a single network). For example, if you log in to Yahoo Messenger as my_account, don't use my_account@yahoo.com when activating the network.
One warning, however - if you attach your personal Twitter account to your Tropo app, every time someone messages you on Twitter, your app will reply. It's better to attach a different account for your testing.
Now that you have the basics of the text channel down, get in depth info on using the ask method to solve a variety of needs.
