Is it similar to this device from Crutchfield?

No, the Crutchfield device is connected in between the alternator output lead.

The Freitag device is connected close to the device that needs to be filtered (i. the head unit). It has three wires; one is 12V in, one is 12V out and the third one is ground. The ground wire needs to be connected to the same ground as the device that needs filtering.

If there's any demand I'll dig the filter up and post a picture of it.