Apple is the king of simplicity. A huge amount of engineering and thought goes into making every aspect of every product — from how the thing works, to how it’s packaged — simple. One could argue that’s Steve Jobs’s greatest gift: taking the enormous complexity out of technology, and making a tool work as it should.

Luckily, lots of companies are finally starting to get this. A smart, new product I’ve been fooling around with lately, the Eye-Fi Card, is a great example. The gadget takes something complex (uploading digital photographs) and let’s you do it simply (on most cameras, via Wifi).  The $99, 2-gigabyte WiFi-enabled memory card goes on sale today at online stores such as Amazon and Wal-Mart.

Perhaps uploading photographs isn’t complex so much as it is too-many stepped and annoying. Either way, people simply don’t do it: Some 4 out of 5 pictures are never uploaded and languish, forgotten, on digital cameras. Eye-Fi solves the problem by converting most digital cameras to WiFi, and allowing them to transmit photos over home wireless networks. The card works on any digital camera that has a slot for an SD memory card — that would be more than 60% of digital cameras out there.

The Eye-Fi Card looks like a garden-variety SD card, but contains a tiny WiFi transmitter. It’s a real feat of engineering, given that the entrepreneurs who founded the company two years ago figured out how to embed a WiFi chip on an SD card without drawing too much battery power or adding an external antenna. Try doing that for under $100. Some half-dozen patents (pending) flowed from that work. (See Fortune writer Michal Lev-Ram’s report on Eye-Fi, “New WiFi camera technology a boon for photo-sharing sites.”)

While setting up WiFi networks can be an exasperating exercise, installing the Eye-Fi Card may be the simplest tech chore I’ve ever performed. It was Apple-like, starting with the packaging: There’s only one way to open the box — via a tiny tab that juts out on the side. Pull the tab and the card slides out on the left side, and a Quick Start Guide slides out on the right side. Follow four steps — which take about two minutes — and you’re good to go.

The Eye-Fi Card slots into a USB reader, which fits into your computer during configuration. (PCs and Macs are supported.) During the config process, you can choose whether to automatically upload your pictures to your computer and to most major, photo-sharing sites, including such Web 2.0 stalwarts as Facebook, Flickr and Typepad. When you’re done with the setup, simply remove the USB reader, pull out the 2-gigabyte card, and put the card in your camera.

The rest is automatic. When you take a picture, it flows to your computer and to any photo-sharing sites you selected, as well as to your free, online Eye-Fi account. It’s pretty fast, too. The picture above was taken with a 5-megapixel Casio Exilim; it took 10 seconds to stream from my camera to my MacBook Pro.

Some tweakage may be required. I had to adjust the power settings on my camera to ensure it stayed awake long enough to transmit the images.

Emboldened by how easy it was to use, I took the Eye-Fi on the road and attempted to add a public WiFi network at a conference, and then my local network at work. Inadvertently, I had stumbled onto two things that the system cannot currently do. The public WiFi network had a “landing page” — as do many sites that offer free Wifi or sell it at airports so users can sign up for the service. Eye-Fi can’t handle landing pages. And in the case of my office wireless network, Eye-Fi can’t deal with so-called transparent proxies — a common protocol used on such networks for security reasons. A company spokesman said that future versions would address those issues.

But for now, the Eye-Fi works quite well on home networks, and you can add as many of them as you can access. I predict this will be a huge hit at the holidays. Indeed, it may be the first holiday season to actually be seen by future generations in too many awful digital photos.