We added a transfer feature to appconference, you can download the patch from sourceforge.

To enable transfer set the ‘CONF_TRANSFER_EXT’ channel variable, for the members you want to enable the feature for, just before joining the conference. Set ‘CONF_TRANSFER_EXT’ to your operator’s extension and when
the member presses ‘#’ in the conference, they will get transfered to that extension.

If the variable is not set, pressing ‘#’ will have no effect so it’s backwards compatible. Don’t need to add any new parameter to ‘Conference’ to enable this feature.