I recently bought a GSM Modem to build a local SMS service. The modem interface is written in Python and implements and processes raw Hayes (AT) commands/response. CLI over SMS is just a toy demo.

I can send "unlimited" SMS for $20/m (Google Fi). However, GSM protocol requires 3-6 seconds per message. So "unlimited" is actually quite limited.

Anyone else playing with modems in 2023?