WISP: Battery-free computer that can be reprogrammed wirelessly

UHF RFID tags harvest all of their operating power from a reader's transmitted RF signal. Multi-access is handled at the protocol layer via probabilistic time-division multiplexing. The tag doesn't actually "transmit" -- rather, it is a cooperative radar target that reflects RF power back to the reader (sort of like an SOS mirror) by intelligently, electronically changing its radar cross section. The tags contain a single IC, and the antennas (for commercial ID-only tags) are roll-to-roll printed... to the tune of Billions of tags per year. The net effect: Tags cost around $0.10 each in volume. The read range is practically limited to around 20 feet, as dictated by FCC limits on the reader's RF output power (1Watt). Nominally, gen2 UHF RFID tags operate at bitrates up to ~500kbps, but there are some specialized tags that can transmit at 100Mbps using just a few microwatts (we used them to transmit dragonfly neural signals during flight!).

Meanwhile, BLE technologies can do push notifications, mesh networking, and the like. The beacon (tag) may contain a full TX-RX transceiver. However, due to the tight spectral requirements of their transmissions, they generally require an external (off-IC) crystal oscillator. The net effect is that BLE beacons are more costly -- on the order of $2-3 ea. This means that they are much less likely to be used to tag everyday items (like a carton of milk) or deployed in the billions for outdoor monitoring.

Source: I'm an expert on these systems as applied to robotics, healthcare, and remote sensing [1,2,3,4]. I'm giving a talk on them next week at IEEE RFID / RFID Live. Oh, and you can also buy WISP-like tags from a company called Farsens.

[1] http://www.travisdeyle.com

[2] http://www.travisdeyle.com/research.html

[3] http://www.hizook.com/blog/2015/08/10/mobile-robots-and-long...

[4] http://www.wired.com/2013/06/dragonfly-backpack-neuron/

Such a thing sounds stupid at first blush, but in combination with ubiquitous inductive charging mats (imagine them on e.g. every desk in an office), it could make for extremely cheap, thin and light e-ink devices—to the point that they start being more like documents than readers: flimsy laminated 'paper' sheets that happen to be able to update themselves.

Heck, if you didn't expect to use them outside of the installation (if they were for displaying internal manifests in a warehouse, or patient charts in a hospital, etc.) then you could externalize all the "document reader" electronics, and just make the device into a dumb framebuffer that hardware in the mat can push images to. (Though you might not need to do this; we can fit some pretty complex logic inside e.g. a credit card, so we might be able to fit all the storage+firmware chips for a full e-reader inside a piece of paper without that making it less piece-of-paper-y.)

Uh. No thanks.

I think the technology has some great potential, but why does every tech article have to dumb everything down into some iPhone analogy?

(Vaguely imagining a completely unpowered electronic lock, and a handheld 'key' that I guess would contain a fairly beefy battery)

Also, this was the first hardware project I worked on where the community used a wiki as the primary communication and it worked! Kudos to Intel

Now, what's the smallest PC you all know that can run for a long time and with some useful work on a tiny, lithium-ion battery? That would be interesting.