> The biggest challenge with the whole setup was finding a SIM from a provider who would let me top it up once per year and maybe send half a dozen texts in that time without deactivating the SIM, for a reasonable price
Good point - so-called "pre-paid" SIMs seem to be hidden subscriptions nowadays. Does anyone have a table of suitable low-usage, long-term SIM vendors?
You might want to say what location you are in for a truly useful answer.
In the UK at least most providers keep the SIM active if it sees some activity in a given space of time¹ irrespective of top-up activity². So if “low” use stretches as far as one text every month or two maybe just have it send an “I'm still here” message regularly. Also acts as a double-check that not getting alerts means all is OK instead of that the alerting service is broken.
1: the GiffGaff one I used for pure data for a week-and-a-half when my landline was down in2020, shut off after three months and a few nagging texts IIRC
2: though if you don't top-up once per month you usually drop onto the basic tariff, so no more “unlimited texts”, but if you are topping up that infrequently that is probably fine
Looking at B2B IoT services is one way to find prepaid SIM plans that don't require monthly top-ups, but usually you have to buy 5+ SIMs so it doesn't necessarily fit the single-device use-case...
Good point - so-called "pre-paid" SIMs seem to be hidden subscriptions nowadays. Does anyone have a table of suitable low-usage, long-term SIM vendors?