(keitai-l) Visiting Japan for 2 weeks - phone, operator & content recommendations ?

Apologies if this is slightly off topic, but I'm visiting Japan for
2 weeks and would appreciate any advice regarding obtaining/using a 
cellphone for those 2 weeks - whether to buy one, rent one, which phone
to ask for, which operator to use, prepay vs postpay etc - bearing 
in mind the following:

a) The primary purpose is to provide my clients (in GSM countries)
   with an emergency number in Japan where I can be reached at all
   times (so, it would be handy to know the number in advance, before
   arriving, but not a pre-requisite of course).

b) I would like to use this opportunity to do some research on the
   end-user keitai experience - from basic web/imode & email to 
   games/iappli etc.

c) I will return to Japan later in 2004, and tend to visit Japan
   once every year.  Since I'm only there for a few weeks throughout 
   the entire year, a recurring monthly contract is not ideal. 
   Are there restrictions on pre-pay packages ?

d) I will be in Hokkaido (snowboarding) but I guess Japan's operators
   have ubiquitous/universal coverage ?

If you can recommend any "must see" content for neophytes then
that would save some time too :)

Thank you very much,

Chas