Ask HN: Most interesting tech you built for just yourself?

Sounds super simple, but was awesome at the time. In the 90s when all of my music was either on CD or ripped to MP3, I built an FM transmitter to broadcast my computer audio (sonique or winamp) to any radio or receiver in the house. It was a perfect solution that didn't take long to implement. I didn't know anyone else who did this.

About 5 years ago, I had a car stolen and lamented what affordable tracking mechanisms I could use. I cobbled together an extra cell phone and a data only SIM. I kept the phone running in the back of my van plugged into an auxiliary cigarette lighter port. It uploaded data to google spreadsheets every 15 minutes. I had to root it to have it automatically boot when connected to power. In the end, it was flawlessly reporting its location every 15 minutes. While I was testing this, my car was stolen. The google spreadsheet pointed me to the GPS location where it was. A phone call to the police and a 40 minute wait for them to arrive got my car back only hours after stolen. Dude was sleeping with a big knife next to him, so I'm glad I let the professionals speak with him.

An app that let anybody convert an otherwise-useless phone into a gps tracker might do well. Those trackers can be expensive.

What kind of battery life would you see with one?

> I kept the phone running in the back of my van plugged into an auxiliary cigarette lighter port.

it's not hard to pull power in a car, just put the phone in any of the sotrage areas or if you're real paranoid with double stick tape up in the dash.