mobileme.
there's an iphone app (for free) and gives you 20GB worth of space.
it's not free (it's £58) but lets you track your iphone, set a passcode if it gets stolen, send a message and play a sound (even if it's on silent), and all this other stuff.
the capability of the email as well is crazy.
you can set passcode locks on confidential emails and you can provide people with downloads that expire after a set amount of time, as well as it being comprehensive push on your iphone.
and the best thing is that it's not just those simple things, you can wirelessly sync all your calendars and contacts to your mac/pc, iphone and your portal just by editing one of them, so you'll have a copy even if you're in hong kong without your possessions.
there's a 60 day trial on apple.com/uk/mobileme - have some fun