I've seen it mentioned a few places but couldn't find a summarized answer on which trains have wifi access, how much it costs, and how to get on. Can someone fill me in/confirm?

What: Wifi speeds on the shinkansen go up to 2 Mbps for download?
Where: I have an impression that it is only on the N700 including Hikari and Kodama between Tokyo and Shin-Osaka.
Requirements: A cell phone that can receive txt msgs is required to get the activation code in addition to the wifi device (802.11 b/c enable laptop/smartphone/tablet).
How: You sign up while still at the station by logging into the wifi portal, paying, and receive the activation code via txt. Then you input that using laptop/phone to activate the internet connectivity on that specific device.
How much: Don't recall the cost.

Thanks!

There is a way around the phone requirement - if you sign up for the Wi2 service (previously discussed here) you can prepay for an access code through their website. They bill it to the credit card you used when signing up.

Softbank Telecom operates Shinkansen wifi.

It has foreign roaming providers list here.

If yours is one of them or it has a contract with any of them, you can use the Shinkansen wifi service.

Thanks! So it is safe to assume that Wi2 would require additional payment for the wifi to credit card on file even if you're currently under a monthly contract/prepaid and a NTT Docomo partner subscription would not be charged extra?