RYNOs single-wheel electric scooter. Self-balancing scooter - its conceivable that commuters could bring one onto a train.
A bit smoother for shorter distances is the self balancing one wheel. This is a solowheel but expect lots of different brands the next years. Even though the computors make an incredible job to keep you in balance on a unicycle, it does take some practise to really get the hang of it.
And last, but not least: Darth Vader on an electric scooter!:)
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