That wouldn't scale because of the range and topology of BLE. Solar-powered micropower 900 MHz modules with built-in microcontrollers would be a basis for a via

That wouldn't scale because of the range and topology of BLE. Solar-powered micropower 900 MHz modules with built-in microcontrollers would be a basis for a viable solution. 900 MHz carries much further for a given power and isn't as susceptible to attenuation due to foilage. Source: did industrial 900 MHz and 2.4 GHz module testing, once upon a time.