I have a remote starter in the car that I'm trying to start from a longer distance than originally conceived for. I have found a way to modify a cell to start the car when getting ringed, but that involves giving money every month to the phone company which I'd like to avoid.
Does anybody know a simple solution to transmit a reliable signal over few hundred meters (through many building walls and the concrete of the parking garage) to a receiver in the car? Ideally I would like to get a ping back that the car has started, but this is optional. If more logic is involved I can use Arduinos on both sides.
I saw somebody mentioning modified walkie-talkies - this will probably be the solution if I can't find anything smaller (I would like to have a small remote starter that would fit in a pocket, but not sure if that would go through all the walls)
Edit I'm looking for a solution that is not very expensive and not very large in size (so I can keep it in my pocket ideally), battery powered, in order to be able to send a start signal few hundred meters away through concrete walls. I don't need high throughput, just few signals. Also not too complex technically so that somebody with limited knowledge (me) can build it :)