My question is this: Are there any recommended phone app mount combos that people have which work well in a range of vehicles?

I'm planning on buying a second phone and mount to use as a road camera. This would mostly be on the east coast of the United States -- Maryland, Virginia, DC, NC, and so on.

My understanding is that leaving the camera on for a long time generally causes heat and power issues, and that I should be prepared to adequately deal with these things. When I searched previous /r/androidquestions threads, however, there wasn't any mention of this, so I'm wondering if it's as big a deal as I thought.

EDIT: In response to "why not just get a dashcam?", two reasons:

1. I drive different rental cars for business, and dashcams are usually too bulky to be portable. There's usually a calibration step that takes a few minutes when you first install them, and I don't want to do that every time I drive.

2. I want to have a high level of control over the data if anything happens, and I'd like it to be backing up to the cloud constantly. I have more certainty that the Android phone will be uploading stuff to the cloud than I do a proprietary dashcam's software.