Roadside textalyzer proposed to determine if a driver was distracted

Oh hell no. They don't need access to your phone to know if you were texting. They could simply query the provider and mandate that they provide a record of outbound text usage within the time frame of the accident.

What is there to protect the owner of the phone from the police for not coming up with another reason to keep the phone? This sounds like slight of hand to be handed over an unlocked phone