Oregon court divides 2-1 on whether seeing a driver look at and touch the screen of a phone creates probable cause that the driver used "a text messaging device or a wireless, two-way communication device" allowing a traffic stop. cdm17027.contentdm.oclc.org/digital/pdf.js… 
The dissent's argument: Today's phones are multifunctional, so you can't assume that tapping away at the screen meant using a messaging service.
Note that the statute has already been amended, and that this case was technically decided under the Oregon constitution's notion of probable cause -- something similar to, but not identical to, the federal 4th Amendment version.
Also, I think the majority's view that the defendant putting his phone down was evidence he was guilty is super weak: This was a really technical case, and most people have no idea about the technical wording of their state driving regulations.
