Look: There's no doubt that "hoverboards" (self-balancing two-wheeled boards) are a huge phenomenon. Celebrities such as "Teen Mom" star Jenelle Evans here looks like she's having a passably good time riding one. But if you're thinking of getting one, we have a lot -- a lot -- of caveats for you.
Let's start with this key fact: Most of the hoverboards you see under the feet of teens right now? Not hoverboards. Unlike the fictional boards seen in the "Back to the Future" franchise (prop shown off here by co-star Christopher Lloyd), what they're now calling a "hoverboard" just balances on wheels. You know, like a skateboard or a scooter. With a cooler name.
A speedy skateboarder can reach a pace of 80 or even 130 mph. (That's the current world record.) Meanwhile, self-balancing two-wheelers can reach maximum of about...10 mph. Which is why British rapper Giggs here is lagging behind Lily Allen after a private movie screening in London.
There have been reports in 2015 of hoverboards combusting or exploding, with much of the suspicion focusing on the large lithium ion batteries required to make the boards move. The batteries reportedly can overheat and explode under rare circumstances.
This photo comes courtesy of the London Fire Brigade, which actually put out a press release in 2015 warning people about the fire risks associated with "hoverboard horror."
"We are warning people to think carefully about buying self-balancing scooters -- or hoverboards -- as Christmas presents," the brigade said. "Major safety concerns have been raised about the batteries, plugs, cables and chargers within some of the hoverboards on sale."
At least one death has been attributed to the challenges of riding a two-wheeled balancing scooter. London teen Nawaf Al-Tuwayan, 15, reportedly fell off the scooter after he had been riding it in the street, in front of a bus. The vehicle then struck the boy and killed him. One witness told a British media outlet that the scooter threw Al-Tuwayan "face-first into the road."
Wiz Khalifa rode his beloved golden hoverboard through LAX airport last summer...a stunt that got him tackled by a team of airport cops.
Six days later, he tried again, this time wearing a suit. The cops left him alone.
Two-wheeled balancing scooters will feel familiar to many an early adopter. That's because their M.O. is quite similar to the 15-year-old Segway transporter; riders stand in the middle and lean in the direction they want to go. Built-in gyroscopes help keep them balanced (most of the time).
In Australia, the state of New South Wales has outlawed them on public streets. They're banned in Mecca. You can't ride them in England or Wales unless you're on private property and have the landowner's permission. Airlines are banning them from flights. And Germany has declared them taboo on public streets.
Complaints about hoverboard safety have spurred the US Consumer Product Safety Commission to launch an investigation. And in the UK, border officials have impounded more than 15,000 of the devices. The officials are citing major safety risks including issues with plug, cabling, charger, battery and cut-off switch, meaning the products don't comply with UK or EU standards.
Super-cheap hoverboards are reportedly going for $300. But most boards range in price from $400 to $1,800.
Amid much hype, Lexus in 2015 introduced the "Slide," a real board that uses a series of magnets and superconductors cooled by liquid nitrogen. The pros: It actually hovers, and it works. The cons: It works in precisely one place. And that's not your driveway.