Yay, message sending.

src/molecules/MessageComposer.js

@@ -3,12 +3,22 @@ var React = require('react');
 var MatrixClientPeg = require("../MatrixClientPeg");
 
 module.exports = React.createClass({
+    onKeyDown: function (ev) {
+        if (ev.keyCode == 13) {
+            var contentText = this.refs.textarea.getDOMNode().value;
+            MatrixClientPeg.get().sendMessage(this.props.roomId, {
+                msgtype: 'm.text',
+                body: contentText
+            });
+            this.refs.textarea.getDOMNode().value = '';
+            ev.preventDefault();
+        }
+    },
+
     render: function() {
         return (
             <div className="mx_MessageComposer">
-                <form>
-                    <textarea />
-                </form>
+                <textarea ref="textarea" onKeyDown={this.onKeyDown} />
             </div>
         );
     },