The Audiovox Universal Tablet Mounting Kit with Built-In FM Transmitter, model IPD-UNVBT, is on one hand, tragically and uncreatively named. On the other hand, it's a product that is exactly what it says on the tin and doesn't waste much time with gimmickry. You've gotta respect that.
The basic kit is composed of two parts: a mounting bracket that attaches to the headrest uprights with a twist on clasp and an adjustable cradle.
The bracket fits a variety of widths for headrest uprights and should fit most, if not all, seatbacks that feature adjustable headrests with thin metal posts. However, the fixed headrests on sport buckets won't make the cut. (To be fair, there often aren't seats in a second row behind sport buckets.) The bracket includes, in its underside, a connection point for the included 12V power adapter, which plugs into your car.
The cradle attaches to the bracket via a tongue that slides into a hidden slot, making both the physical and electric connections. This allows a bit of telescoping and tilt adjustment to accommodate viewing by adult and child passengers of a variety of heights, but holds the tablet firmly in place while the vehicle is in motion.
On either side of the cradle's body, you'll find one of two powered USB ports for high-speed tablet charging. Total the output is 3.4 amps, which is shared between the 5V ports, which should be enough to charge a mounted cradle and one other accessory.
The cradle's primary function is to hold a tablet while the car rolls and bounces down the road. It does this with an adjustable grip that features a trio of stubby arms. The lower two arms are fixed in place, while the central upper arm slides up and down to release and hold a variety of tablet sizes. The release/lock for this adjustment is located on the back of the cradle. Pull up to unlock the arm, place the tablet within the cradle's adjustable grip, and then push down to lock everything into place. It's simple enough, but the release/lock's location on the back of the cradle could make it difficult to reach behind a larger tablet.
The arms feature a generous, thick foam-rubber lining to protect your device's finish.
Built-in FM transmitter
Just above the each USB port is a small, unlabeled 3.5mm analog auxiliary input that feeds audio to the cradle's integrated FM transmitter. The transmitter automatically powers on when a patch cable is plugged in and automatically powers down when disconnected.