In this early part of the 21st century I see we are finally beginning to move towards the very infancy of this kind technology and here are a few of the monitoring devices I have tried:
Hear Rate Monitors:
The Zephyr Heart Rate Monitor is a Bluetooth enabled heart monitor that can pair with Android device and from there utilize an app to provide a real time heart rate monitor. One issue is Bluetooth uses a fair amount of power (requiring recharge a few times a weeks) and I have yet to find any gym equipment that utilizes a Bluetooth connection- so data is only available to the Android device it is paired with.
DigiFit sells a module that connects into the data port of an iPhone/iPod Touch/iPad that allows the unit to connect to ANT+ enabled devices (such as heart monitors). It also allows publishing workouts to Facebook/eMail/ and retrieves data from Zeo sleep monitors/Withings wireless scales/FitBit (coming soon). ANT+ is a low-power standard for transmitting data and many of the newer gym machines can utilize this protocol.
Polar and Nike+ also offer a WearLink+ heart strap monitor, but it is limited for use with the Polar watch ecosystem plus a few iPod Nano devices (some needing the additional Nike+ module). One benefit is that it can also utilize the Nike+ foot pods that go in/on your shoe to add a pedometer for pace measurement.
The FitBit is a clip on device with a digital accelerometer that keeps track of your walking steps. Additionally, holding the button enters a bedtime mode where it tracks movement during sleep. The charge on a FitBit will lasts about two weeks of use. It will wirelessly upload the data it accumulates when you are in range of the base/charging station. One concern for the FitBit is that it is small and doen't have a hard clip; I have lost (and eventually found) this device four times in the past year.
The Jawbone Up is very similar to the FitBit but it comes in a bracelet format (this eliminates my 'easy to lose' problem). It also has a vibrate notification that can be set via iPhone/iPod Touch/iPad app to remind you or to act as an alarm clock (this works very well). This currently works only with iOS devices and you must plug the Up device into the headphone jack to sync activity/sleep info; Wireless would have made this device a winner.
Additionally, the last few generations of iPod Nano devices and the Nintendo 3DS feature integrated pedometers. Not much to see here- please move along...
The Zeo Manager is a EEG headband that you wear on your forehead during the night. There are two flavors; A desktop clock version with a SD card for data storage (i.e. manual upload) and one that utilizes Bluetooth with a connection to an iOS/Android device running the Zeo software. The headband will monitor and graph the time you spend in deep sleep, light sleep and REM; It is much more precise than the aforementioned FitBit or Up devices as it uses an EEG to monitor electrical activity in the brain instead of relying on nocturnal movements for determining sleep zones.
The WiThings body scale is a WiFi enabled scale. It will post your weigh-in to the WiThings page (also available for viewing via iOS/Android app) as well as post to Twitter or Facebook (if so desired). It performs additional measurements for BMI, muscle or fat content. It is pretty accurate for weight as it has four independent feet and it can be required to reset zero before each weigh-in. It will record your weight in pounds, kilograms or stones...
So far all of these devices are external gadgets that monitor biometric data from external effects. Hopefully in the next decade or so we will advance in the realms of neuroscience and genetic engineering to be able to directly interface with the body's electrical signaling network. I am sure the military is already doing such as this- but once it becomes consumer ready (and affordable) I will be one of the first in line for the more advanced sub-dermal augmentations. :)