What do you call these new gravi bikes?

Trying to google all sorts of combinations but can’t find them. I think you know the ones I mean, they work without any apparent source of energy. No motor, no battery, no pedals, nothing, you just shift your weight and they move. It uses gravity, but words like “gravitation/antigravity” etc haven’t worked. I’m not even sure if they’re called “bikes”. You stand on them and they have 2 big sidewheels.