Need Wifi and the ability to send out a voltage (or close a circuit)

Hello. Thanks in advance for your reply.

I'm looking for the smallest and hopefully cheapest board that has wifi (it could be a base board with an addon as long as its not too expensive) and it needs to be able to to close a circuit/send voltage. (I dont know the exact voltage, yet)

I want it to interface with another legacy system which I why I need it to be able to send voltage/close a circuit. (This is how it will communicate, albeit simple and one-way) to the host system.

If I understand your post correctly, WiFi Shield and this Uno Board should do the job. Have you done anything with Arduino before?

I suspect you'll find that a clone with integral WiFi will work out cheaper than a UNO and WiFi shield.