StatusNet emits activities already for all status updates. See:

http://evan.status.net/api/statuses/user_timeline/1.atom

<?xml version="1.0" encoding="UTF-8"?>
<feed xml:lang="en-US" xmlns="http://www.w3.org/2005/Atom" xmlns:thr="http://purl.org/syndication/thread/1.0" xmlns:georss="http://www.georss.org/georss" xmlns:activity="http://activitystrea.ms/spec/1.0/" xmlns:media="http://purl.org/syndication/atommedia" xmlns:poco="http://portablecontacts.net/spec/1.0" xmlns:ostatus="http://ostatus.org/schema/1.0">
 <generator uri="http://status.net" version="0.9.1">StatusNet</generator>
 <id>http://evan.status.net/api/statuses/user_timeline/1.atom</id>
 <title>evan timeline</title>
 <subtitle>Updates from evan on Evan Prodromou!</subtitle>
 <logo>http://avatar.status.net/evan/1-96-20090919144027.jpeg</logo>
 <updated>2010-04-17T18:34:30+00:00</updated>
<author>
 <name>evan</name>
 <uri>http://evan.status.net/user/1</uri>

</author>
 <link href="http://evan.status.net/" rel="alternate" type="text/html"/>
 <link href="http://evan.status.net/main/sup#1" rel="http://api.friendfeed.com/2008/03#sup" type="application/json"/>
 <link href="http://evan.status.net/main/push/hub" rel="hub"/>
 <link href="http://evan.status.net/main/salmon/user/1" rel="http://salmon-protocol.org/ns/salmon-replies"/>
 <link href="http://evan.status.net/main/salmon/user/1" rel="http://salmon-protocol.org/ns/salmon-mention"/>
 <link href="http://evan.status.net/api/statuses/user_timeline/1.atom" rel="self" type="application/atom+xml"/>
<activity:subject>
 <activity:object-type>http://activitystrea.ms/schema/1.0/person</activity:object-type>
 <id>http://evan.status.net/user/1</id>
 <title>Evan Prodromou</title>
 <link rel="alternate" type="text/html" href="http://evan.status.net/"/>
 <link rel="avatar" type="image/jpeg" media:width="449" media:height="449" href="http://avatar.status.net/evan/1-449-20090919144027.jpeg"/>
 <link rel="avatar" type="image/jpeg" media:width="96" media:height="96" href="http://avatar.status.net/evan/1-96-20090919144027.jpeg"/>
 <link rel="avatar" type="image/jpeg" media:width="48" media:height="48" href="http://avatar.status.net/evan/1-48-20090919144027.jpeg"/>
 <link rel="avatar" type="image/jpeg" media:width="24" media:height="24" href="http://avatar.status.net/evan/1-24-20090919144027.jpeg"/>
 <georss:point>37.7749295 -122.4194155</georss:point>

<poco:preferredUsername>evan</poco:preferredUsername>
<poco:displayName>Evan Prodromou</poco:displayName>
<poco:note>Montreal hacker and entrepreneur. Founder of identi.ca, lead developer of StatusNet, CEO of StatusNet Inc.</poco:note>
<poco:address>
 <poco:formatted>San Francisco, CA, USA</poco:formatted>
</poco:address>
<poco:urls>
 <poco:type>homepage</poco:type>
 <poco:value>http://evan.prodromou.name/</poco:value>
 <poco:primary>true</poco:primary>

</poco:urls>
</activity:subject>
<entry>

 <title>Wow, Windows Live is doing awesome stuff with activitystrea.ms. #streamcamp</title>
 <link rel="alternate" type="text/html" href="http://evan.status.net/notice/18829"/>
 <id>http://evan.status.net/notice/18829</id>
 <published>2010-04-17T18:28:17+00:00</published>
 <updated>2010-04-17T18:28:17+00:00</updated>
 <link rel="ostatus:conversation" href="http://evan.status.net/conversation/116439"/>
 <content type="html">Wow, Windows Live is doing awesome stuff with &lt;a href=&quot;http://activitystrea.ms/&quot; title=&quot;http://activitystrea.ms/&quot; rel=&quot;external&quot;&gt;activitystrea.ms&lt;/a&gt;. #&lt;span class=&quot;tag&quot;&gt;&lt;a href=&quot;http://evan.status.net/tag/streamcamp&quot; rel=&quot;tag&quot;&gt;streamcamp&lt;/a&gt;&lt;/span&gt;</content>
 <category term="streamcamp"></category>
 <georss:point>37.7829847 -122.389693</georss:point>

</entry>
<entry>
 <title>@dbounds Good to see you here!</title>
 <link rel="alternate" type="text/html" href="http://evan.status.net/notice/18828"/>
 <id>http://evan.status.net/notice/18828</id>
 <published>2010-04-17T18:26:10+00:00</published>
 <updated>2010-04-17T18:26:10+00:00</updated>
 <link rel="related" href="http://cliqset.com/user/dbounds/KFINrVEDAR6Azgee"/>
 <thr:in-reply-to ref="tag:cliqset.com,2010-04-17:/user/dbounds/KFINrVEDAR6Azgee/0" href="http://cliqset.com/user/dbounds/KFINrVEDAR6Azgee"></thr:in-reply-to>
 <link rel="ostatus:conversation" href="http://evan.status.net/conversation/116438"/>
 <link rel="ostatus:attention" href="http://cliqset.com/user/dbounds"/>
 <content type="html">@&lt;span class=&quot;vcard&quot;&gt;&lt;a href=&quot;http://cliqset.com/user/dbounds&quot; class=&quot;url&quot;&gt;&lt;span class=&quot;fn nickname&quot;&gt;dbounds&lt;/span&gt;&lt;/a&gt;&lt;/span&gt; Good to see you here!</content>
 <georss:point>37.7829847 -122.389693</georss:point>

</entry>