Here's the question: does a device exist that can act as a wifi to Ethernet client that can automatically connect to more than one wireless network based on priority?
Here's the reason: I live in a situation where there is a weak, fairly slow wireless connection (Connection 1) in an adjacent building, which I am allowed to use. The signal is not strong enough for all devices to use it. I'd like to pick this signal up and serve it to the various devices in my flat, including some that are Ethernet-only. However, when I'm at home I can also use my phone with tethered 3G (Connection 2) which will be faster than Connection 1. I have an Asus RT-N16 tomato router. I'd like to get a wifi to Ethernet device, in client mode, plug it into the WAN port of the RT-N16, and then serve the flat with the RT-N16. I'd like the AP to be connected to Connection 1 by default, but to use Connection 2 when it is available. That way, I walk into the flat, turn on 3G tethering, and immediately my whole flat is using the Internet from my phone (Connection 2) rather than the adjacent building (Connection 1).