Are content observers persistent in Android? If I create a content observer in an activity, will that observer continue to run until I remove the observer.

Basically I am creating a service for SMS, where on receive and on send I post the SMS out to a web service, so I can check my messages with out having my phone.

If the content observer is tied to the Activity's life, how can I create a ContentObserver that will always receive notifications on content:/sms/