Do these communicate via cell networks, as in cellphone providers, or just point to point between arduinos? I'm looking to have emergency notifications texted (or other techniques) to a cellphone without the weak-links of needing power company and cable company to be operational.
Where does one go to get service for GSM? (assuming it's available in the US) Does it mean signing up for a pricey cellphone contract with one of the 'bigs' like Sprint, AT&T, etc?
All I see regarding discussing these is in getting them to operate, not the bigger picture of using them.