I'm in the process of moving in to a bus. I have a number of devices that want a permanent network in place, however I want the ability to connect the bus to OTHER wireless networks in order to receive internet access and pass that on.

Basically my ideal scenario is I have my phone autoconnect to wifi when it's around the bus, allowing me to control lights/power/inverter etc, and can then access a web portal by which I point the bus router at another wifi network (for example while parked beside a friend's house) and log in to that network and using it for web access.

I am a capable tinkerer, with enough coding knowledge to look at someone else's code and tweak it to work, but probably not build anything new. Is there a raspberry pi/Linux package that allows something like this? Any obvious solution to look towards?