We are going to expand osom functionality soon.
First, we will add direct replies @username. There will be button to create such reply in web. The same functionality in sms, will be achieved by creating message that starts with @username - e.g. @vita sometextsometextsometext
2nd, we will add one more emoticon (trollface) and a special button "!".
Posting with "!" creates urgent message that goes immediately to all your friends. Initially, we will allow one URGENT messages per day. If it becomes popular feature, we may consider selling extra "!" credits.