LONDON — All marketers these days want to deliver ads across as many screens as consumers have available to them.

Doing so is increasingly easy, thanks to a growing plethora of advertising technology. But measuring the impact of those deliveries remains a thorny problem.

Tantalized by the possibilities, some in the industry are dreaming of a single, unifying metric that could unite ROI across all those devices. But others think that is unrealistic as yet.

“It’s becoming more and more a question clients ask,” Mindshare UK CEO Helen McRae tells Beet.TV in this video interview. “We’re getting better and better at it.”

But McRae isn’t bold enough to claim she has cracked it: “There is no common currency. The data from source isn’t comparable, that’s the first challenge. We need to get that right first.”

McRae isn’t yet buying in to the idea of a holy-grail metric. All devices are different, and each client’s campaign objectives are different.

“We just need to get on with it and start doing it, even if it’s imperfect,” she says. “We’re going to have to live with several (metrics).”

This video was produced at the Future Of TV Advertising Forum. Beet.TV’s coverage is sponsored by Xaxis. You can find more Beet videos from the conference on this page.