As a result of the deal, IMMI will now be known as Audience Measurement Technologies, Arbitron said in a brief statement.

Further details about the acquisition are sketchy at the time of going to press, but Arbitron did say that one of the technologies it has acquired in the deal is IMMI’s cellphone-based technology, which collects information on cross-platform media usage by detecting audio signatures.

The news follows yesterday’s unveiling of Arbitron’s new Portable People Meter (PPM) 360 device, which is a smaller, more cellphone-like evolution of its previous PPM design, incorporating wireless technology.

It is yet to be seen whether the redesigned PPM will improve compliance among certain demographics, particularly those in the 18-34 age group where the company has historically had problems, but almost three years ago now Arbitron’s then-CEO Steve Morris floated the possibility of incorporating media monitoring software into cellphones as one way to resolve the issue.

“There are problems with cellphones as a research tool, so we are, and have been for quite a while, working with cellphones as a potential device, and I think there could be a solution there,” said Morris. “Long term, we’re open to anything that could fundamentally improve and increase the performance in any one of those cells, so… it may be part of the future.”

IMMI’s technology is a patented proprietary software platform that respondents download to their own smartphone or a smartphone provided to them. According to IMMI’s website, the phone randomly samples ambient audio in the room several times a minute, tracking exposure to TV, movies and radio. In addition, IMMI software monitors mobile web surfing activity and measures internet use.

IMMI last hit the headlines when its joint venture with Nielsen to measure out-of-home TV viewing was scrapped in last 2008 because of a lack of interest from clients.

In January 2008, Kantar Media Research led a $25m round of Series C funding into the media measurement firm.