I actually found this thread after googling for hours, it was nice to confirm that you can activate the bmobile cards for 10 days at a time using landline, because I won't have a Japanese mobile and I'm only there for 3 days (so there's no point waiting for the snail mail card).

rookiecz, from what I've seen this appears to be the two options for short term stays:
b-mobile SIM U300 (purchase online only, deliver to hotel) - 2980 yen (http://www.bmobile.ne.jp/sim/index.html)
b-mobile 1G (can be purchased at Yodobashi Akihabara or BIC Camera) - 3480 yen (http://www.bmobile.ne.jp/1gb/index.html)

Both are activated the same way. OP is referring to the 1G card. If you don't need more than 300 kbps transfer speed, you can save a few bucks but need to arrange for delivery of the U300 SIM/microSIM to your hotel.