There are basically two kinds of so-called lazy people's fitness, one is electrical stimulation. A kind of vibration.
There are different views on electrical stimulation. But it is mainly used for recovery, and it is impossible to directly produce abdominal muscles by this. Some do improve muscle and strength. It was popular abroad a long time ago and is said to have been used in Bruce Lee. But people who achieve this effect are also harmful to the body and need to cooperate with great movements.
Vibrating muscles can't fool anyone. It is generally used to reduce fat, but it is also deceptive. Most fat people will feel effective after using it, but in fact, the effect is not to reduce fat, but to dehydrate. It is normal to replenish water every day and then make it up.
So don't listen to the publicity. It's all bullshit It's not useless at all, but it can be used as an auxiliary prop reasonably.