Having travelled to Japan several times over the last 2 years, one of the thing I found frustrating was a lack of SIM cards for voice calling. This can be useful for calling restaurants for reservations, checking schedules for the trains and buses within Japan that runs very punctually and even to keep in touch with friends that are travelling with you when you go to separate destinations. I purchased a b-mobile SIM card for data once, and it was nice to get connected online but the data does not allow video call or Skype, though the data functioned well enough and was provided by NTT Docomo.
Today, over the e-mail, b-mobile actually sent me notification about their new product, the PAYG SIM in addition to their Visitor SIM, that offers both voice and data. For those interested to see the comparison of the 2 products by b-mobile, head here. The PAYG SIM is valid for 7 days, includes 60 minutes worth of local and international calls, and 3GB of data usage. But the catch here is that it costs more than twice of the visitor SIM that offers 1GB of data over 14 days.
For ¥9,980 (or ~US$100) the voice and data SIM is certainly expensive. But for foreigners, that does not leave them much choice as I understand getting a local plan is not a viable option for foreign tourists, thus I believe this product is the only one of its kind to allow you decent telecommunication capability without paying excessive roaming charges. Though you would not be saving much anyway!