Great teaching aid, I didnt use the 16" but rather the 12" wheel for my 3 year old daughter. She has never used a training wheel in her life and at this point she rides 3-4 mile rides with us every weekend. She was off and riding on the first try and we used the gyro wheel for about 2 weeks. After my daughter had a few days under her belt with the gyro wheel, we began to forget to turn it on, so my daughter didn't need it anymore. So it came off. My 2 year old is next.
Here's the trick... Start your kid on a "scoot bike" at 2. They are two wheelers with no pedals and no training wheels. You can get them in wood or metal, doesn't matter, just get one low enough for the kid to stand over. The kids walk them, then they start to "Fred Flinstone" on them and next thing you know they are flying around on the scoot bike, picking up their feet and turning, fully balanced. When they are tall enough to stand over a 12" bike, at around 3, start them on the real bike with the gyro-wheel. If your daughter is like mine, they will take off riding.
Once a kid has learned balance on a scoot bike, it is actually dangerous to put them on a bike with training wheels. The reason is that the child has learned how to "lean" into a turn in a balanced fashion. Training wheels prevent them from leaning into a turn, and actually force them to lean OUT on a turn, which can cause them to flip off the bike. Gyro bike does not prevent the natural balance/lean process at all.