What's the most futuristic piece of tech you can buy for under $100?

A COVID vaccine (offer not good inside the US)

5 months of an OpenAI subscription

Amazon and Walmart have microwaves under $100

lighters. fire on demand! for all of preindustrial human history these things would be worth more than gold

A full working computer, more powerful than what we used to go to the moon, and using less power than a light bulb.

It can take many forms, like smartphones, SBCs or older PCs/laptops.

I think the deauther watch is pretty cool if we're thinking cyberpunk-esque

https://dstike.com/products/dstike-deauther-watch-v3s

Still this thing, 20 years on:

Raspberry Pis and other microcomputers can be had for pretty cheap, and they can be put to a surprising variety of tasks. You need to be a bit of a jack of all trades to fully embrace that DIY element, but I'd bet that showing off a project that you mostly built yourself would be seen as futuristic by most people.

A smartphone

Anything with GPS capability

A knife. Futuristic in that it will be handy for hunting and self-defense after the future collapse of civilization that results from our insatiable appetite for consumption - of, among other things, useless gadgets.

Devices less sophisticated than smart phones were once pretty common in sci-fi novels, but they still achieved the same sort of thing, all the world's knowledge in the palm of your hand.

You can get smartphones for absurdly cheap these days, and while crappy by modern standards they're still technological marvels.

If you shop around you can find a Brother (B&W) laser printer for about $100.

Imagine this weird future: Printers that always just work no matter what type of computer you have or how long they've sat since you last used them. And the "ink" cartridges last forever. And you can buy 3rd party refills or even refill them yourself. Plus it's completely reliant on microplastics to do its job, what's more futuristic than that?

3 sea shells.

A 1-terabyte MicroSD card

I feel like that really depends on how you view futuristic.

I think things with colored e-ink displays, USB C chargeable AA batteries, handheld emulators, 2230 NVMe drives, and USB C power portable displays are really cool but I feel like their availability these days has made them lose a bit of their futuristic luster. They would have blown my mind when I was a kid.

More niche products like Meshtastic and ESP32 Marauder devices are things I view as futuristic (and can be found for under $100).

A bow drill fire starter.

...I suppose it depends on what you assume the future will be like...

Barring that, you can get some small vials of tritium gas for under that price.

Probably a cheap 3D printer

An R36s is like 40 bucks, and can emulate a LOT of old game consoles. I think that's pretty neat

I once found a curved 4k monitor at my local thrift shop for $70.

You can buy a cheap smartwatch that will monitor your pulse, give you a pulse oximeter reading, handle text messages and phone calls, take photos, and also within a reasonable margin of error check your blood sugar for about $35 on AliExpress.

£76.77

Bluetooth headphones/headset/earpiece. You too can look like Uhura from Star Trek by sticking a wireless speaker in your ear!

what is “futuristic” in this context?

A calculator is pretty futuristic depending on where you start

A basic DNA test can tell you your ancestry back thousands of years and identify numerous genetically determined traits. It's kinda crazy what kinds of things they can tell you about yourself.

A Voxellab Aquilla FDM printer. They're regularly on sale for about $70. Maybe cheaper these days since they're kind old now.

you can get several smart outlets around your home for that, have fans and lamps and humidifers etc all remote controlled even with your voice.