The GPS shoes have a tracking device implanted in the right sole, with a GSM/CDMA antenna snaking up behind the heel so that the GPS signal is not blocked by the body; the shoe also includes a USB port, primarily for charging the product’s battery.

Made by footwear company Aetrex, with GPS technology provided by GTX Corp., the shoes cost $299.99, with the added monthly cost of a tracking plan. Caretakers can opt to have the wearer’s location recorded every 10 minutes for $39.99 a month, or every 30 minutes for $35.99 a month.

Customers can visit the Aetrex Web site to purchase the shoes, set up an account for the shoes through GTX Corp. and, using Google Maps, create a “geo-fence” encompassing what’s considered a safe distance around a wearer’s house or living community. The caretaker can opt to have messages sent via email or receive simple SMS text messages on a cellphone when the wearer wanders outside of the geo-fence.

The caretaker can then access the online portal to find the wearer’s location on a Google Map. There’s also an emergency backup system the caretaker can call for additional help; that requires the caretaker to share the GPS information with the emergency-care provider.

Aetrex began planning and designing the GPS shoes two years ago; the product was certified by the Federal Communications Commission in September of last year and began shipping in late December. Only a few hundred pairs have sold so far, but Aetrex president Evan Schwartz said the companies have done little marketing at this point, and have been focused instead on a strategic rollout of the shoes.

Schwartz also said the company will begin shipping to Canada and other countries soon, and that Aetrex and GTX have struck a deal with an international SIM card provider to make the tech available internationally.

For now, Aetrex and GTX are selling the shoes directly to consumers, but they have been in talks with the Alzheimer’s Association and the Veterans Benefits Association to explore partnerships for marketing the shoes to assisted-living communities and geriatrics departments.

While the GPS shoes could give caregivers some peace of mind if a family member is prone to wandering, the concept of trackable clothing could raise questions from both a technical and legal standpoint.

Aetrex says the battery life of the shoes lasts two days on average, but the shoes would be rendered ineffective if a caretaker wasn’t around to charge them, or the wearer forgot to do so. Also, if the person monitoring the shoe-wearer opts in for more frequent pings, the battery will die more quickly. Aetrex says the GPS shoe system does send email or text notifications to remind the caretaker when the battery is getting low.

There’s also the possibility, of course, that the wearer could remove the shoes, or simply refuse to wear them.

When someone purchases the GPS shoes and goes to activate the online monitoring system, he or she has to sign off that they are a designated caregiver, and that they have the authority to monitor the wearer of the shoes and make those kinds of decisions for the wearer. But, as with many of the technologies we have at our fingertips, there is always the possibility of misuse.

A recent Supreme Court case involving law enforcement officials’ use of GPS to track a drug-trafficking suspect has also raised some questions about the rights civilians have when it comes tracking others using GPS technology (our Wall Street Journal/SmartMoney colleagues did a good rundown of some instances where it can be done legally). Stories like these indicate that we’re still in the early stages of setting privacy standards when it comes to digital tracking.

“It’s all kinds of good and bad and ugly popping up when it comes to GPS tech these days, and that’s definitely a concern,” Schwartz said. “There are enough people who make jokes about tracking a spouse, or what if you threw the shoe in the trunk of someone’s car and they never know it’s being used for that, that sort of thing.”

“But at the same time,” he added, “this shoe has been designed to serve a purpose, and it’s to help caregivers, so we have a hard time believing someone would abuse this.”

Correction: An earlier version of this article said the GPA shoes support CDMA technology. The shoes do not support CDMA; the antennae in the shoes are GSM/GPS.

In Google terms, I cheated by copying off more established rivals. However, as Bing might put it, I just added a few new inputs to my coverage algorithm.

In any case, here’s what I learned overall. Barcelona is filled with pickpockets. I’ll need comfortable shoes to navigate the vast trade show and chase after said pickpockets. There’s way too much going on, so I should give up now. The food is amazing, but I will be too busy to eat any of it and should pick up some candy bars now.

On the news front, expect a lot of stuff on tablets, as well as interesting new gear from Samsung, Sony Ericsson, HTC, LG and China’s ZTE.

Here are some other specific tips I pulled out of the many awesome emails, for which I am deeply grateful. To reward those who shared their knowledge so generously, I have pulled the following out of context to present the more humorous ones and saved the most useful ones for myself.

From Mobile Industry Review’s Ewan MacLeod:

“Whatever you have actually planned, cut that in half and you might end up completing it. On my first year I booked about 40 interviews all over the place in different halls. By 11 am on Monday I was screwed.”

And:

“Phone signal is typically rubbish. It’s a real pain when people are trying to demonstrate things. Expect 2G/GPRS and if you get 3G, it’s a bonus. With thousands of people on-site, each with 2-3 devices, it’s no surprise the networks can’t handle it.”

From TechnoBuffalo’s Noah Kravitz:

“Pickpockets are no joke. Listen to what your Mom told you the first time you were in a big city as a kid, and stuff your wallet way the heck down your front pants pocket when you walk on the streets. Seriously. And avoid big crowds of swarming people suddenly hell-bent on getting cozy with you. No joke.”

From CrunchGear’s Greg Kumparak:

“Eat everything you can find. The food is rarely disappointing.”

From Eric Zeman of Phone Scoop:

“The Fira (where the event takes place) is a whacked-out maze, and is confusing. Study a floorplan ahead of time, or find an official map/floorplan that you can download to your phone. It takes longer to get from place to place than you might think, because there is never a direct path. Give yourself enough travel time in between meetings.”

Between November 2008 and March 2009, Redmond hired away five Yahoo veterans. First, Sean Suchter, VP of search technology at Yahoo, left to become general manager of Microsoft’s Silicon Valley Search Technology Center. Then Yahoo search scientist Qi Lu followed him after being tapped as president of Microsoft’s Online Services Group. Soon after that, Larry Heck, former VP of search & advertising sciences at Yahoo Labs, accepted a job in the R&D department of the software giant’s online services division. Jan Pedersen, who once served as a chief scientist and VP of Yahoo’s Search and Advertising Technology Group and Dayne Sampson, Yahoo’s VP of operations for search and advertising, followed.

Now comes word that three more Yahoo execs have taken jobs at Microsoft (MSFT). Knut Risvik, Yongdong Wang and Kevin Timmons, all Yahoo veterans, are now headed to Microsoft.

Risvik, once a chief architect at Yahoo (YHOO), will work on Microsoft’s search platform and infrastructure. Timmons, formerly a Yahoo VP of operations, has been charged with running the company’s data center expansion. What Yongdong Wang, once a VP of international search, will do remains to be seen. He is, however, reporting to Harry Shum, Microsoft’s corporate vice president for search product development, so presumably he’ll be doing something similar.

A nice little trifecta for Microsoft and one that surely inspired Yahoo CEO Carol Bartz to drop a frustrated F-bomb or three. As I said back in March: If Yahoo employee defections to Microsoft continue apace, there may come a day when Redmond will no longer need to buy the struggling company’s search business. It will already have acquired it.

But–as many readers have requested–they will all be available in their entirety in this column.

In the less contentious spirit of DEMOfall and TechCrunch50, two demo conferences taking place simultaneously this week, we’re happy to bring you all the demos we had onstage at D6.

Here’s part two of the conference’s most popular demo, with well-known inventor Dean Kamen, who showed off his latest creation, the “Luke Arm” prosthesis.

The state-of-the-art bionic arm looks and feels to its user like his or her native limb.

The video of the demo is in three parts, all of which I will post all today.

In this video, the DEKA Research founder and Segway creator talks more about how the arm’s control was designed and how it was received by a group of injured veterans.

Kamen also talks about the FIRST Robotics competition, which he started to get young people interested in science and technology.