For now, however, electronic tags like this are still in their earliest stages of development. This new tag, developed by researchers in Sweden and the U.K., doesn't do much more than turn on. It's slow to respond—it takes about 10 seconds—and it practically needs to touch a cellphone to do just that. Still, the tag has a couple of impressive features. It's durable, lasting for more than two years, the researchers reported in a paper published today in the Proceedings of the National Academy of Sciences. In addition, while it's always a challenge to power small electronics with equally small batteries, this tag has a unique solution for that problem. The tag actually captures a portion of nearby cellphone signals and powers its display with that signal.