The black antenna measures 4.25 inches and has a magnetic base for attaching to your car's roof. The connecting cord is 12 feet long, so you should have plenty of room for threading out your door or window, even if the arrangement can be a bit awkward.
The power cord measures about 12 feet with a small DC converter near one end. That's probably longer than you need to connect to your car's power port, so you should take care to tuck the slack cord away. The cord uses a mini-USB port to connect to the cradle.
You will need to leave your iPhone in the cradle to get the boosted signal, which means you'll need to use the speakerphone or a Bluetooth headset to make calls. But really, you should be doing this anyway when you're making calls while driving. Unlike the Griffin Clearboost, you can't take the iBooster on the go, but the trade-off is a better product.
When testing the iBooster in low-signal areas of San Francisco we did get a noticeable signal boost when making calls. Calls were less likely to drop, and the connection remained strong when passing through the dead zones.