Yes, I recently purchased 2 of them for a trip to WDW. They worked out great.
I have twins that just turned 3 when we went. They are very small for thier age.
We did a
DCL cruise then stayed on property at WDW, so no rental car and I didn't want to deal with 2 car seats.
The straps work as advertised. They are very easy to install. There is 1 loop that goes around the back of the seat...... You do have to bother the person behind the child to lower their tray table to install/remove it but it shouldn't get in their way after that.
From the loop around the back of the seat, 2 straps hang down and go to the standard seatbelt. Then there is the standard car seat clip in the front that goes across the childs chest. There are plenty of pictures on their web site so you get the idea.
I have to admit the straps appear to be very high quality, similar to the airline seatbelt material, but the clip across the chest seemed pretty cheap.
My kids had no problem wearing them. It was similar to the car seat straps that it wasn't like it was totally new. But then again, they got to sit in a big people's seat so they liked that.
They aren't cheap by any means (~$75). I don't know what the laws are for when a child "needs" to be in a car seat versus just a lap belt. For us it solved my wife's concern of safety flying with toddlers and they were small/easy/light for me to deal with.
They definately worked out for us and now we'll have them for the next trip.
Feel free to reply or send a PM if you have specific questions.
Jeff.