HTTP Delivery Reports Polling 2
The return object looks like:
<sms_deliveryreport>
<data>
<messageid></messageid>
<deliverystatus></deliverystatus>
</data>
<call_result>
<result>True</result>
<error />
</call_result>
</sms_deliveryreport>
Your delivery status will be displayed between the "deliverystatus" tag.