1. It's good you are doing your research. Do not spend a $ until you know exactly what you want.
2. Wifi is not possible the technology you want is Zwave
. Stay away from X10. Zwave is wireless mesh network, the more devices you have the stronger it gets.
3. I prefer Leviton Vizia RF+ Zwave switches and dimmers because they are the most robust and reliable but they are also the most expensive. But you get what you pay for!
4. After that to use our Lightswitch app you will need a USB Control ThinkStick plugged into a PC.http://www.controlthink.com/
5. You will need THinkEssentials software that you can purchase with the stick to set your whole network up.
6. Then you simply need to run our server application or this more advanced one called ZVirtualScenes to control your devices from the iPhone.http://code.google.com/p/zvirtualscenes/