Nielsen claims it has successfully completed a technical trial with CBS and Syncbak to measure mobile TV viewing — and could eventually track usage on other apps, including Aereo’s controversial service — but the research firm says there’s still considerable work to do before that data can be incorporated into TV ratings.

Nielsen worked with CBS, which is a strategic investor in Syncbak, to record viewing on iPad and iPhone devices with four CBS-owned television stations in New York and Los Angeles: WCBS, WLNY, KCBS and KCAL. The two-week trial ran from end of April into May.

“With the success of this trial we now know we can obtain measureable credit for the in-market mobile viewing of our content and do so in a way that is monetizable,” CBS chief research officer David Poltrack said in a statement.

CBS has not decided whether to offer live TV on mobile devices as an authenticated service — limited only to subscribers of partner pay TV operators, as ABC is currently planning to do — or to deliver it free to anyone.

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To participate in the Nielsen test, Syncbak had to integrate Nielsen’s software development kit into its app, which let Nielsen monitor viewing of the broadcast nets via an ID3 tag.

“Our goal is to be able to measure content wherever it is used, on whatever device,” said Farshad Family, senior VP of local media product leadership at Nielsen. “We are doing these tests to further develop our technology, so we are able to scale it as the ecosystem provides more content.”

The challenges, though, include obtaining demographic info from mobile TV viewers and whether Nielsen would integrate mobile TV into its regular television panels. “The industry has to resolve all these questions,” Family said.

When fully activated and deployed, the Syncbak app is designed to let users watch live, in-market broadcast TV on Apple and Android smartphones and tablets. The startup’s technology is designed to provide TV Everywhere authenticated access to local TV to subscribers of participating cable and satellite providers.

Nielsen may at some point work with Aereo to measure viewing on connected devices, but the research firm has no specific timing, according to a rep. Aereo, whose investors include Barry Diller, is being sued by large broadcasters alleging the startup is engaged in blatant copyright infringement; Aereo says its service, which uses tiny remote antennas, simply lets customers access free over-the-air TV in a new way.