If you're familiar with Tetrax's line of products, then you likely recognized the XWAY model right away. But if this is the first time you've ever seen that big black X with the gold square in the middle, then you're definitely wondering how the heck it works as a mount.
There are more photos and a couple of videos that should make it clear below, but it breaks down like this: you stick a small magnetic disc to the back of the EVO, then you clamp the X onto your car's vent by twisting the knob in the center, and you place the phone on the X so that the disc and magnets (the gold rectangle) meet.
The neodymium alloy magnets are said to "create an attraction power equal to 750 g, resisting to more than 5G acceleration strength"; they're very strong, in other words.
Here's a user review of the XWAY demonstrated on a HTC Droid Incredible that should give you a better idea of how it works.
The Tetrax XWAY is made in Italy and can be yours for $35.99, free expedited shipping included.[eBay] Thanks, Brandon!