Even with the ubiquity of smartphones and their usefulness for navigation, automakers don't design dashboards specifically to accommodate them, leading to a variety of adhesive and suction cup mounts on the market. However, it turns out that the simple air vent, given its proximity to a driver's hands, makes for a good smartphone mounting point.
At least, that's the thinking with Infernal Innovations' vent-mounted magnetic smartphone holder. The mount uses rubber prongs to clip onto the louvers of a car's air vent, and its magnetic face holds smartphones firmly in place.
This vent mount is very simple, consisting of circular magnet about 2 inches across and half an inch thick. Protruding from its back are four tapered prongs made of rubber for flexibility. The mount's packing includes a rectangular metal plate and an adhesive circle. That plate is included because your smartphone is not likely to stick to the mount's magnet on its own.
Magnet mounts aren't uncommon for smarphone holders, and they have the advantage of making it easy to attach and detach your phone, without having to deal with a clamp. However, the fact that smartphones are not generally magnetic requires a bit of adjustment. I could have used the adhesive circle included in this vent mount's kit to glue the metal plate to my phone, but that would have been ugly. Instead, I inserted the metal plate into a plastic case that neatly fit around my phone.
With plate in place the phone held very firmly through the case's thin plastic to the vent mount's magnet. Without too much effort, I could pull the phone loose.
Installing the vent mount into a car proved quick and easy. The prongs have one thin and one larger slot--I chose the larger and slipped it over the car's vent louvers. With the magnet looking like a button on top of the vent, I attached my phone and took a drive. At the vent position, I could easily see the phone for turn-by-turn navigation. Using the touchscreen wasn't much of a problem, but as the louvers were vertical trying to touch the phone's main button to activate Siri made it pivot to the side. I could only maintain the phone's position by bracing the phone with one finger behind while I simultaneously pushed the button in front.
Vent movement is an inherent problem with vent mounts. I previously found with a different product on a car with horizontal louvers that the weight of my phone caused the vent to droop down. To use a vent mount, your car will need to have either stiff or appropriately oriented louvers.
Another issue with vent mounts, again not specific to this one by Infernal Innovations, is that your phone sits in the way of the hot or cold are blowing from the car's climate control. In most cars, you can turn off the vent, but then lose some of the car's climate control capability, or leave it on and either heat or cool your phone, either of which might not be good for it.
As an alternative, Infernal Innovations also makes a suction cup magnetic smartphone mount .
The Infernal Innovations Vent Magnetic mount holds a phone firmly, isn't too expensive and works well, after considering the general caveats for vent mounts above.