This plugin is a standard plugin as of 7.00.166.00.
It adds a button to the toolbar of the report viewer "Email". When pressed a new email form is opened with the report output attached as a PDF. The user just needs to add the recipient address, subject and message and then press the save button to email the report.
Attached is the plugin for those who can't wait for 7.00.166.00. If you choose to customise it, make sure you copy the plugin once imported, or subsequent upgrades to the Jiwa database may undo your changes.