I've been using my Montar smart phone mount when I drive, but it has been so blistering hot in Los Angeles lately that the sun's rays coming through the windshield are overheating the phone, causing it to shut itself down.
I was given a Kenu Airframe+ Leather Edition car mount ($40 on Amazon) to try out. It clips onto a car's heating/aircon vent. Because I have the air conditioner blasting at all times, it keeps the phone cool. The phone feels a bit more wobbly than the Montar, but it has not yet bounced out of the Kenu's spring-loaded grip, so it's not a big deal. If the temperature ever drops below 90 degrees F again, I will probably switch back to the Montair, but for now, the Kenu is what I need. Read the rest