You probably thought your Uncle Henry was a little weird (and annoying) when he kept showing you how many more Nike FuelBand calories he needed to burn/earn to reach his preset daily goal. But what’s amazing is how that little wrist band with its tight feedback loop displaying points can actually motivate people to improve their lifestyle. Oh, it also makes a nice watch.

We’re at the dawn of a new industry loosely called "wearable technology" that may have reached $4.6 billion in sales around the world already this year.And Google Glass isn’t even for sale yet. Many geeks already are on board. The April Modis Geek Pride Survey of people aged 18 or over found that "61 percent of self-described geeks said they would buy and wear a smart watch," and "56 percent would do the same with smart glasses." Perhaps even more interesting, 37 percent of non-geeks were also interested in smart watches, and 35 percent were interested in smart glasses.

The biggest market in wearable tech is health and fitness.

Wearable tech gadgets are already widely used by individuals to track information related to health and fitness. In addition to FuelBands, there are Jawbone Ups and Fitbits, which also let you know how you're doing on your fitness goals. There are even smart socks that let you know when you're too sedentary and when your running form needs improvement.

Beyond measuring calories burned or steps taken, wearable technology can already provide persistent monitoring of a patient's vitals or fetal and maternal heart rates, gauge the severity of sleep apnea, or vibrate when slouching is detected.

Organized sports are a major outlet for the technology already. This year, a limited number of NFL football helmets will be equipped with sensors to gauge the impact of blows to the brain and to determine whether different positions get different types of impact. Many colleges, including Virginia Tech, are also using sensors to study how and why some players suffer head injuries and others do not. The findings might lead to rule changes. The TSG Hoffenheim soccer team in Germany has placed sensors in shin guards, in clothing, and even in the ball to collect data on ball possessions, speed averages, and more. That data can then be used to customize training to target the strengths and weaknesses of each player and to reduce the risk of injury.

The next wave of wearable devices expected to hit the market may be smart watches. ABI Research forecasts 1.2 million smart watches will be shipped in 2013 due to the wide availability and low cost of micro-electro-mechanical systems (MEMS), energy efficient connectivity technologies such as Bluetooth 4.0, and the high penetration of smartphones in many world markets, which supports a flourishing smart watch app ecosystem. While Apple struggles to bring its iWatch to market, Samsung has already begun to ship its Galaxy Gear smart watch, which includes a 1.9-megapixel camera and a speakerphone, comes in an array of colors, and shoots 720p HD video.

While wearable devices interweave technology into everyday life, making technology pervasive and the interaction with it frictionless, there are some obstacles to widespread acceptance of wearable technology.

Power: Wearable devices still need to be charged, so you remain a slave to your charger station. Most current wearable devices only work in conjunction with your smartphone, which means at least two devices must be charged. When the two sync, they'll drain even more power. And power management will be a critical issue with wearable devices. All the "low power" warning signals might overwhelm that marathon meeting when you intended to lock the door until the job was finished. Perhaps Nikola Tesla will still teach us a thing or two about powering these devices via skin conduction from a central power unit, which might be housed in your shoe and powered by simply walking.

Theft: If your wearable device is going to fulfill its obvious role as the key to your digital life, you'll want to be able to limit who can use it. How soon will we get voice detection that is genuinely secure? How soon will we get a fingerprint reader that can’t be hacked? (You probably read the claim by the German group that they bypassed the iPhone 5S’s fingerprint scanner on Apple's first day of record-breaking sales of the phone.)

Privacy: This has already become an issue surrounding Google Glass, and these products have yet to hit the market. How will you feel around someone wearing them, knowing they might videotape everything you do and say? Should they be banned from restrooms, locker rooms, boardrooms, and bedrooms? Will the police or a victim be able to subpoena your personal video if they think you saw something unlawful? Technology now makes it possible for your mate to watch everything you do. What about hackers who find their way into your wearable mobile hub and have access to all the images flowing through the device?

Functionality: There are already complaints about the functional limits of many of these devices. They will need to be more flexible in the future to accommodate a variety of sensors to measure vital signs and whatever's going on in the wearer's vicinity.

Too much info: While sensors now are focused primarily on giving you more information about your life, it will not be long before technology worn by others will be able to gather information about you. Would you want someone to monitor your pulse rate changes to see if you were stretching the truth a little? How will you be able to build a data or sensor firewall around personal technology?

The miniaturization of computers that you can wear on your body for a variety of functions took another quantum leap recently when Stanford engineers moved beyond silicon chips to build a basic computer using carbon nanotubes. This eventually means smaller, faster devices with more capability and the possibility of introducing computers inside your body, not just hanging on the outside.

Just as smartphones moved technology and communications off of the desktop and into your hand, there is every reason to expect that wearable technology will eventually replace smartphones. While having the Internet in your hand seems like a miracle now, to our kids--who may see it from glasses or hide it in their jewelry and operate it with just a few gestures--physical texting and pushing a button to receive a phone call will be so "last century."