Residents worried about mobile phones can now use the internet to keep track of the level of emissions from masts.
The joint project between Vodafone and Oxford City Council - named Cassiopea - will record emission levels in the Cowley area of the city.
This data will then be made available as a graph on the council's website, compared to the recommended maximum.
Authorities say the small mobile unit - which is solar-powered - will be moved to other areas of Oxford in the future.
The machine will detect Electro-Magnetic Fields (EMFs) from all sources, not only mobile phones but also origins as diverse as taxi firms and baby listening devices.
Jane Frapwell, who is running the project for Vodafone, told the BBC News website the company had provided training and information to the council but was taking a back seat.
"We've consciously decided to do that, so people can be reassured it's independent," she said.
"Obviously people have huge concerns about mobile phones.
"We thought if people could check themselves - on a weekly basis if necessary - the actual levels against the World Health Organisation maximums then that could provide some reassurance."