Before the N900, I was carrying at least two devices simultaneously, sometimes three, sometimes even four:

A siemens A55 for phone and SMS



A Palm TX for PDA, music player, PDF viewer, gaming, and (rudimentary) navigation



As the Palm has no GPS built in, additionally an external GPS:



And a Canon Powershot G5 for photos:



All now included in the N900. I'm only on the lookout for a good digital compact camera to make better photos than the build-in camera.