Neutron Economy has found a reporting site for radiation levels all over the nation of Japan, it's called the System for Prediction of Environment Emergency Dose Information (SPEEDI).
We have no readings for Tokyo, but we do have some in Kanagawa Prefecture (thank you GNF - Global Nuclear Fuel), which is right next to it. You can also get 7-day graphs of dose. But each monitoring station is different and there are 12 of them in Kanagawa Prefecture, and it turns out that matters a great deal to both the background dose and the profile of the elevated radiation levels. I apologize for the quality, but here is my mashup.
The levels of radiation are the area underneath the fluctuating line. It is not the height of the line but the area underneath that is the dose. The overall dose is what would effect health.
Link to the partially translated System for Prediction of Environment Emergency Dose Information (SPEEDI)
Readings of a geiger counter in Tokyo. Thanks to a reader
Some translation of radiation readings from the Ministry of Education radiation monitoring sites.
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