Yes, I have read about that too. You must notify your passengers that their audio is being recorded so that you are not illegally recording what they are saying.
It depends on your state's laws. In the state I'm in, only one party being recorded must be aware of it - so if you're in your own car, and you know you're being recorded, you're good. You don't even need to tell a police officer (although it is polite to do so, and may serve to calm down the officer, too.)
If you loan your car to someone, you would have to either disable audio recording, or let them know they're being recorded. In my state, it's only illegal if nobody being recorded knows their being recorded. (So you can't wiretap someone
else's phone, but you can record your own phone calls all you want.)
And in general, it only applies to audio recording - almost everywhere allows silent video recording in public with no notice.
That said, to answer the original question - I don't have a dedicated dash cam, but I do have a phone holder that hangs from my windshield that, when I have my iPhone in it, the iPhone's rear camera nicely points right out the windshield, with a view of my speedometer, too. So I generally record from my phone, and if nothing worth keeping the recording happens, I immediately delete it when I get to my destination. The most interesting thing I've caught on it was a deer crossing the road. (And a few "bad drivers," but nothing that caused an accident.)
I also sometimes set my other phone (I have one for work, and one personal,) in my cup holder, pointing at me and out the driver's side window, to record out the window if an officer pulls me over. I haven't had to use those recordings for anything.
