I asked my Criminal Investigations teacher - a Michigan state trooper - about this. He didn't know anything about the cell phone DED or the ACLU's demands, but he said he's "sure there's some device out there," as he put it. (He's an informal fella.) He also reiterated that a search warrant is needed before phone records can be searched and that "fishing expeditions" for information are frowned upon.
The MSP released a press release, yesterday, due to the public uproar the news report caused. Here's a portion: "The department's internal directive is that the DEDs may only be used by MSP specialty teams on criminal cases, such as crimes against children. The DEDs are not being used to extract citizens' personal information during routine traffic stops."