Clip your smartphone to a vehicle air vent with this Logitech [+] trip 989-000119 mount that features magnetic coupling to securely attach your device to the mount. The compact, ergonomic design helps reduce clutter and allows comfortable viewing.
It works really well and it's sturdy and strong. The only thing I don't like is that it blocks the vent from moving and directing air. I think that maybe if it were a bit longer it might've given the vent more room.