March 2026
I'm a big fan of not giving out my phone number for some random service I've used once. Yet my phone only has one SIM slot.
This is where my trusty, 11 year-old phone comes into play. With an increbible 5.74 GB of internal storage, and a gigabyte of RAM, I figured why not use it to run an OTP server? (I had a sim card handy, so that was what we were going to use.)
I'm comfortable with TypeScript APIs, but the problem arises with the fact that I have never written a native Android app before - especially for Android 6.0.0 (released September 2015). Thankfully, sillicon valley's golden child - OpenAI, had just released GPT-5.4, so I decided to take it for a spin.
The rough idea is simple: keep the device permanently online, push a quick POST request on incoming SMS messages, and make it accessible as an API without having to manually check the phone each time.
I decided to first write the backend, and then have the model write the app around that.
The rest of the article is coming soon...