For business, nothing comes close to a Blackeberry with BES (Business enterprise server)
I dont have one because my main business software is only compatible with Windows mobile.
I could write it all down but I have a brochure that explains the benefits of a Blackberry
Just remember to get the most out of them you need BES and not BIS.
BES is true exchange sycronisation meaning your secretary can book/move appointments using her outlook on your calendar and the changes are instantly synced to your workstation/webmail/blackberry
Send an email on your desktop, it appears in the sent items of your phone.
Send an email from your phone and it appears instantly in your sent items on your desktop/webmail.
It also uses your actual email address unlike something like BIS whic needs a forwarding address in the background.
Its also instant email communication (no more hitting send and receive) or waiting 5 mins.
Its bullet proof and uncomplicated and just works.
** Re the 4 year old, I dont know of any models that will live through being hidden in a glass of milk, best form of defense is a location they cannot reach.