the N900 has multiple connectivity :

* GSM
* Wifi
* Bluetooth
* ...

The Offline disable all these connectivity.
If I want to received GSM calls, I have keep the device Online.

So wifi connectivity is activated and the devices automaticaly connects to known access points.

To spare the battery, it would interesting to select what to disable in the Offline mode.
So, all connectivity could be disabled except the GSM.

http://maemo.org/community/brainstor...line_profiles/

David.