As an alternative to Michael's solution you can also replace:

{{block type="wpsync/getpostcontent" template="wpsync/getpostcontent.phtml" wpurl="http://localhost/about"}}

With

{{block type="getpostcontent/getpostcontent" template="wpsync/getpostcontent.phtml" wpurl="http://localhost/about"}}

Notice the change in the block type. The first part of the block type is defined by this in your config.xml

<blocks>
        <getpostcontent>
            <class>Elevated_Wpsync_Block</class>
        </getpostcontent>
    </blocks>

As an alternative to Michael's solution you can also replace:

{{block type="wpsync/getpostcontent" template="wpsync/getpostcontent.phtml" wpurl="http://localhost/about"}}

With

{{block type="getpostcontent/getpostcontent" template="wpsync/getpostcontent.phtml" wpurl="http://localhost/about"}}

Notice the change in the block type. The first part of the block type is defined by this in your config.xml

<blocks>
    <getpostcontent>
        <class>Elevated_Wpsync_Block</class>
    </getpostcontent>
</blocks>