Fitbit and google sheets
Having little knowledge about databases at the time, I was able to find a script that authenticated with Fitbit and then saved information into Google Sheets. I used the built in features of Sheets to run the script every night, giving me an updated data source that I accessed with the Sheets API. I used this to create a few different data visualizations.
College vs. The Real World
My first ever data visualization project (and my most popular by far) looked at my minute-by-minute step data from Monday to Friday. The top area was my weekly activity over 80 days of college and the bottom was my activity after graduating and getting a "real job". Each bar is a minute with the height and color determined by the number of steps. 1440 bars with a very low opacity make up a day, and overlaying days increases density that forms patterns.
I shared this on the subreddit /r/dataisbeautiful and it climbed to the #1 post on the sub and received 800,000+ views on imgur.
Weekends vs. Weekdays
Using the same technique, I looked at a friend's data over three years, grouped by weekday and weekend. Clearly he has a 9-5 job. What was most interesting to me were the two accumulations of low intensity areas around 7AM and 9PM. The morning one coincided with his average wake-up time while the night pattern coincided with him getting ready for bed. From this I could tell the average time he spends in bed (or stationary) before going to sleep.
An abstract sleep study
What started out as a tech-driven exercise in d3.js turned into a very abstract visualization of several people's sleep patterns. This is a good example of how confusing data viz can be and that making something animate in a "cool" way should never be the focus of data viz. I could explain it on here, but it's confusing even to me. This served its purpose in teaching me the right things to focus on while creating data viz tools.