How about a call back system? No need for huge strings of numbers to punch in..
I just found this service recently.
One Handed Apps
As I understand it, you set it up on your PC or mobile phone or both.. when you want to make a call, go to the url (on PC or mobile phone) and trigger a call. The service automatically calls the number (from your preset favorite overseas numbers) and then calls you back on your office, home or mobile depending on what you trigger and the number has already been dialed.
But I think it is around the cheapest cost per minute for overseas calls. Don't just use in Japan but can set up where ever you are on your PC - but can only use the i-mode model in Japan.
charges
Seems a heap easier to me as I tend to call the same overseas numbers all the time and dialing them in everytime was annoying.
Hope this helps