For what it's worth, here's my take on gadgets, as I used and abused them during my "lose weight slow!" diet program:

. I got a FitBit and quickly gave up on it. It wasn't telling me anything I didn't already know. The MyFitnessPal app (and there are lots of equivalents), on the other hand, was quite useful. They crowd-source their data, making it very easy for you to find damn near anything. Sometimes it's hard to come up with a reasonable estimate, particularly if you're eating at a fancy restaurant where the food is creative and unusual, so you ignore it and move on. After you've been doing calorie counting for a couple months, you "get it" and don't really need the app any more.

. I used to have a home scale that tried to electrically measure your body fat. It might as well have been a random number generator. It's more important to have a scale that's accurate and has big digits I can read without my glasses. (Whoever designed the "Thinner" model I'm now using had a strong case of iPhone minimalist design envy.)

. When running, I've found my heartrate monitor (a cheap Polar unit) to be very helpful. I've learned that if I let my HR get above 170 bpm for too long, I'll be a zombie for the rest of the day. If I slow myself down to keep my HR at 160 or lower, then I'm fine. Also, lots of treadmills these days are compatible with the Polar transmitter, so if I'm stuck in a hotel gym, at least I've still got all the data on the screen in front of me.

. I keep an Excel spreadsheet, wherein I dutifully type in the date, my weight, and any data from my heart rate monitor (when running) or my stopwatch (when swimming, I separately time myself for each set). When I'm traveling, I'll use gmap-pedometer.com to map my runs, and the hyperlink goes into the spreadsheet. About once a month, I'll invent some new way to dork around with all of this data. For example, I have a lovely graph of "heartbeats per mile" over time, which you can see trending downward. It's a nice proxy for how my fitness has improved.