I bought a pack of these a few years ago, they are NOT wireless, but use three tiny button cells. I’m posting here because I think it might be of interest to people who find Norm’s video above interesting. The cost of the whole pack is less than it would cost to buy the batteries, so you can consider them disposable. I had one that the batteries ran out, and I just pulled them from another unit. They are fun to, for example, throw into a helium party ballon, or Japanese lantern.
I have built them into door deadbolts and gate latches to show when they were not locked or fully-closed. Batteries last for years in that kind of application. Obviously requires some ingenuity with mechanics and wiring, not an out-of-the-bag solution. I built one into a mailbox to show when the mail was delivered, but the batteries only last a few hours max so that project was scrapped.
These actually are “wireless”. Though you have to include that in quotes because they do in fact have quite a bit of wire in them. But there’s no internal power source or physical connection to an external source. Instead there’s a simple coil of wire attached to the LED. If you watch the video in the first link from the OP, you’ll see the person holding the wireless LEDs in her hand has her hand positioned over a large copper-wire hoop. The LEDs use induction to produce power that’s being radiated by that big coil. There’s no physical connection - the power goes through the air.
Used to be, something like this was considered unusual. Now, with all the cell phones that come with wireless charging, it’s becoming ubiquitous.