Jason Crane, I've started wearing a little clip-on bluetooth connected dongle from Fitbit.
The device itself is quite small and I barely notice it clipped to my shirt - how long until it goes through the washing machine?
It records how many steps I walk each day plus how many floors up climbed. If you wear it at night (they have a wrist strap that makes it comfortable) it records how "efficiently" I sleep.
The device stores data until synced over bluetooth 4 (very low power) using an app - I'm using the iPhone app which is good but crashes rather a lot at the time of writing.
The app uploads the recorded activity to a web site where it can be graphed in even more ways than in the iPhone app, plus you can friend people and enter in to a bit of friendly competition.
I am over weight although thankfully not "obese" at this stage. Wearing the tracker does motivate me to climb the stairs where possible and walk to the shops on the weekends.
Bluetooth 4 is a good technology. The device lasts all week even though it's listening for a connection from the phone app at all times.
This week I purchased the Fitbit scales. They connect to the home Wifi network and by simply standing on them it measures my weight and uploads it to the site. The most impressive bit (for me) was how it was configured and given the details of my Wifi network by running an app on my computer. I'm not quite sure how this was achieved as clearly scales don't have much of an input device.
Of course Fitbit isn't the only game in town, there's Nike, Jawbone, Basis, Striiv, Larklife and many others.
All this current interest in wearable computing, like Google Glass and the rumoured Apple watch, are good things if they help us to avoid turning into the blobs like in the Pixar Wall-E movie. Computers have freed us from physical activity, now hopefully they can help us stay active enough to live.