I'm always surprised by the things people have built using Google Sheets or on top of Google Sheets such as sheet2site or Tiller. It made me wonder what other things people have built or used it for.
I can't say it's terribly impressive, but I've collected my performance at 90% of my gym visits over the last two years. Sheets has been very convenient in keeping myself on-track. I'm thinking about taking a weekend to clean the data and graph some trends or normalize my rep counts/distance/times into a single index I can use along with my weight to quickly assess "how I'm doing".