Search for "M2M" (machine to machine) communications. There's a lot of this going on over old 2-way paging networks. It's how the non-vaporware "Internet of things" works. There are thousands of air conditioning compressors, refrigeration units, elevators, pumping stations, and other boring but important pieces of infrastructure sending their short messages every few minutes. Often they're plain text, something like "Pump 1: OFF. Pump 2: ON. Inside temp: 71. Outside temp: 52. Faults: NONE." There are little M2M modules for such communication. They tend to be rugged, reliable, and cost a few hundred dollars.

Some of these use cellular service. There are special low-data-rate M2M plans for this. AT&T charges $3.33 a month for 1MB/month if you pay by the year. If you have a protocol that doesn't bloat its data traffic by using HTTP, HTTPS, XML, JSON, and other data hogs to send a few bytes of payload, this works out well.

There's something new called LoRa.[1] This is a standard for low-bandwidth wireless network devices with a claimed 10 mile range. Data rates range from 300 bps to 50 kbps. They run in the 900MHz ISM band, so they have good building and foliage penetration, although the range then drops to a claimed 2-3 miles. Units start around $56 on Digi-Key. There are Internet gateways available, so that many of the little cards can be connected to the wider world.

[1] https://www.lora-alliance.org/