It does (Local Notifications) but to set those the app would need to check for new email and if it finds any create the notification. AFAIK on iOS it can't check for the email in the background, the app would need to be open (removing the need for the notification).
Email snoozing needs some kind of backend, but it doesn't really need access to your GMail account credentials. The backend could just re-send you the email normally.
