Good points however I won't be charging w the truck parked and off, climate control will be in use 99% of the time unless its cool enough without and it will not be on the upper dash. The coils will be under the little plastic cubby with the rubber mat on there as well and have a good 15mm between them and the device to disperse heat. The charging pad that I'm cannibalizing has active cooling, a slot type fan similar to what you'd find in a mac mini or small laptop which should keep the temps pretty close to ambient under the console. The device will warm at times a bit which is normal with charging. It's worse when using wireless because of the efficiency of indiction chargers but not being right on it, based on tests I've done on my desk should keep it no more warm than a USB charge would. I will of course keep an eye on it. Being android in my case, there are plenty of system apps to see battery and CPU temps. Being android auto and the HU I'm installing also supporting miracast I'll pretty much always have my phone display off which keeps the heat down during use/charging considerably.
I work in the wireless industry and I'm quite familiar with all of the tech and its limitations. I used to work as a rep for Samsung so I'm aware of how bad a situation involving an overheated battery or device can get. Those Note 7s... lol.
It would be wise if anyone does this to probably not wire it to a constant 12v as a safeguard to keep it from charging in case it was left in a closed vehicle in full sun and also not drain your battery if forgotten for awhile, as unlikely as that is being a phone it could still happen. The vehicle ambient temp would be on the high range to cause most phones to shut down due to overheating even if not charging. This is why I'm tapping into that power port circuit as itll be a low current draw and not interfere with the obd circuit and it'll shut off w the ignition.
The remote start I'm installing supports the ability to auto start in low/hi temp thresholds so I can always program that into the safe range of what the battery is designed for if I wanted a fail safe. It wouldn't be the most efficient thing fuel use wise but better than a burnt phone/car. If it started up I'd be notified pretty quickly via an LTE module in the dash and know to go out and retrieve my phone. I have the house setup with a lot of smart home gear and it would see device not inside the house w geolocation data and tbay coupled with other triggers that should happen once I come inside I can set a notification that would alert on my watch or hue lighting. It's a bit excessive but doable.