i just wrote some code for a twitter API in j2me, this is the basics of what you need i think
public void updateStatus(
String data) {
HttpConnection con = (HttpConnection) Connector.open("http://twitter.com/statuses/update.json");
once we have this connection, linked to the url in question we can set a few request properties which are needed by the site
con.setRequestProperty("Content-Type","application/x-www-form-urlencoded");
con.setRequestProperty("Content-Length",""+data.getBytes().length);
con.setRequestProperty("Connection", "close");
OutputStreamWriter ow = new OutputStreamWriter(con.openOutputStream());
wr.write(data);
wr.flush();
}
The call to the above method should be something like updateStatus("status=this is a status @ptay89&in_reply_to_status_id=4051308780");
the data is the stuff you post, fieldName=fieldData&fieldName2=fieldName2data and so on, as a String
Sorry if that doesn't work, very basic as i said
Phil