Can I start a service when I get a text message or an email (when there is a Notification) or should the service already be running and it should react to the Notification?
You can intercept text messages with SmsInterceptor (Phone library). In that case you will need to start the service and then call StartForeground to prevent it from being destroyed.
I would also like to know is there a similar way to intercept email messages, phone calls and Talk chats.
What I'm going for is a kind of alert that goes on every so often when there is an unread message or phone call missed.