I would like to turn on my car's heated seats over a mobile/cellular network using my iPhone, and I'm trying to figure out the simplest path. I know very little beyond that goal, but I know that RF, ...

As you can see in the schematic the 12V battery (or use other voltages) is connected with the plus at terminal T1 and minus at terminal T2. The contact 1 and 4 are connected together as 2 and 3 are ...