Android : How to know when an email is sent with Android Gmail app and who is it sent to?

I'm interested on building an app that knows when an email is sent with Android's Gmail app and to who is sent.

Since there is no plugin API for the Android Gmail app the only method I've found to do this is capturing outgoing packets that use the SMTP protocol. Using this method will I be able to identify emails and read their destinatary? Or will the destinatary be encrypted under SSL?

Are there other ways to do this?