I have a "collect now, find time to make sense of it later" approach. I DO NOT have time to make sense of it, but if I can do minimally or non-invasive tracking, I'll have the data to tear through later. Some tracking in itself induces behavior change, but in general, I haven't made the kinds of breakthroughs that are possible when bringing all of this together for myself, not to mention what would happen if we brought the same data for 100M people together.
I use the following tracking tools on a daily basis:
http://myzeo.com (I've used both the Mobile and Bedside products. Mobile product is available at all BestBuys locations. Mobile automatically uploads data, deskside requires you to sneakernet an SD card to your computer for upload. iPhone Mobile app is functional, but ripe for improvement (new product)) Full API, even as much as getting full EEG data from serial port on bedside product. I don't sleep without it.
http://fitbit.com – I love my Fitbit. I have personally purchased 6 of them. That's right, $600 worth of pedometers. Is that endorsement enough? Unfortunately crippled API. Only daily stats available, no intraday yet, although they say they're working on it. There are some Perl/Python frameworks that slurped data from Flash graph sources, but my attempts last night to use the Python one failed. I don't step without it. I also carry it in my pocket and always have a leash on it. The "leash" I link to fits precisely around the fitbit. Since the strap is tucked into my pocket the gaudy URL printed on it isn't visible. I haven't lost or broken a single fitbit since. My four year old has even been able to hold onto one for a few weeks so far.
http://withings.com – I have both the scale and the blood pressure monitor. Both work well. I haven't used the API directly, but it's highly integrated with many other services. I use the scale just about every day, BP cuff every once in a while. Need to enable the BP reminder…
Visiontac VGPS-900 – a GPS datalogger that is simply great. It takes an SD card and records a CSV every 1 (or 10) seconds with lat,long,alt,heading,elevation, etc. The feature that really jumps out though is that it also records GPS delusion of precision information so you know how accurate your data is. I simply drop it in my pocket every morning and plug it in to charge when I go to bed. It will take a 2GB SD card, but after about a year of using it every day, it maxes out at about 1GB of usage for some reason. Also, it has bluetooth, so you can use it as a bluetooth GPS dongle for a camera, Android phone, etc.
http://dailyburn.com – Great for exercise and food tracking. They seem to be moving to some sort of 24/7 fitness video channel or something, but haven't given up on their former tracking business yet.
http://mint.com – I track my financial transaction automatically with this great product brought to us by my employer - Intuit, Inc.
http://goslice.com / http://lemon.com – Both are receipt tracking apps. Lemon wins the receipt entry battle with the ability to take a snapshot of a receipt with your iPhone. However, Slice wins in every other category. You authorize Slice to scan your gmail/yahoo inbox and it automatically grabs receipts from Amazon, Intuit (yep!) and others. You can also scan and email receipts to them and they'll OCR (only tried once, but it did work). The real reason I LOVE Slice is that it sees the order all the way through. It knows when I place an order with Amazon. It picks up the ship notification and then tracks it with the carrier. On my Phone I have a list of everything I ordered, everything that has shipped and everything that's been delivered. I get a push notification when I have a delivery arriving and it tells me which items will be showing up in each of those deliveries. It's hot sauce!
http://spotify.com / PandoraJam in conjunction with http://last.fm – Just about every track of music I listen to gets "scrobbled" to last.fm. I can retrieve a timestamped record of every track I've listened to (4200 + and counting). I'm actually working with some graduate students at UCSD and Carnige Mellon to take my last.fm data and my fitbit data to see which tracks make me move the most. I have a personal goal to move more and I want to put the songs that make me shake my moneymaker into heavier rotation.
http://rescuetime.com – Agent runs on your PC/Mac/Android device and records what app and doc you are working on. You can then categorize each app/doc into a project or type of work (communication, development, projectX, projectY, etc). Huge potential here, but I haven't spent much time on it.
http://posturetrack.com – A MacOS app that uses your webcam to track your posture. It logs to CSV every minute with the % time in good, okay, bad and away postures. Also can chime to get you to sit up straight. It has potential to provide input to heuristic estimate of presence/location with the "away" metric.
Google Latitude – I use the Android App. Haven't put it to much use. Mostly rely on automatic checkin feature for Work/Home, but sometime check in manually.
I use these tools less frequently:
http://runkeeper.com – I've started using this on walks. Works also for hikes, bike rides, running (obviously) etc. It uses the iPhone/Android GPS to log your exercise. Nice app to take along on a run alone.
http://tallyzoo.com – They've let their app lapse in the Apple App Store, but it's a pretty okay service for tracking # and time of occurrences of an event. For instance, I would just tap one button every time I filled my water bottle, every time I took an Advil, etc. Stopped using this tool when I decided to stop invasive tracking.
http://www.tonicselfcare.com/ - Just started using this sporadically. I used to track this with TallyZoo, and now that I only take one supplement regularly and no regular prescription medications, it's less interesting. However, I WANT to be tracking this sort of thing. I also want to be tracking random symptoms somehow to be able to relate side effects to my taking some supplement or prescription drug or another. E.g. The cure is worse than the disease.
A word about food tracking:
Tracking food is very painful. Maybe it's because I eat a lot. It's certainly more difficult because I don't eat a lot of processed foods, so what I eat doesn't come with a bar code that I can scan. I only track food intake sporadically for a day or a week before giving up again. None of the offerings I've found track the ingredients of the food you're eating. That's something I'd see value in for determining low-grade food allergies.