IMMI, a San Mateo, CA-based mobile-based ad tracking and research firm, has raised a big $25 million in its third round of funding. The round was led by Kantar Media Research, the media research division of WPP, one of the world’s largest ad holding groups. Existing investors Draper Fisher Jurvetson and Advanced Technology Ventures also participated in the round. IMMI’s service involves arming consumers with cellphones that are then used to track TV and radio ads they watch and hear…this works automatically as long as the phones are turned on.

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The IMMI phone randomly samples 10 seconds of room audio every 30 seconds…these sample are uploaded continuously to the IMMI servers. IMMI also tracks all local TV and radio outlets, and then compares mobile-uploaded signatures with the IMMI-monitored TV and radio broadcasts. The mobile phone also receives a signal from an IMMI “Bluetooth beacon” when the panel member is at home, so the servers can interpret media exposure as “in” or “out-of-home”.

IMMI CEO Tom Zito previously founded videogame company Digital Pictures and Garageband.com.

More details in release.