Design a Wi-Fi device to control 4 electrical equipment (230V AC / 50 Hz)

I want to design a Wi-Fi device to control 4 electrical equipment (230V AC / 50 Hz) with dimming facility, can be fitted in existing switch board and electrical appliances connected with it can be controlled with switches even the our Wi-Fi device is off or not working/inoperative (I know that we cannot control electrical equipment’s using Mobile during this condition but it can be controlled by normal switch). Working functionality In normal condition: It can be controlled using mobile and normal switch simultaneously. If I start a fan/bulb using mobile then also it can be turned off using normal switch, then again I can start the fan/bulb using mobile even it turn off manually using the normal switch. Means the normal On/Off switch of our switchboard can be worked as two ways switch when it connects with our Wi-Fi device. In Wi-Fi device inoperative condition: If suppose our Wi-Fi device may not working because of some reason all the electrical appliances which are connected to the Wi-Fi device can be controlled by the normal switches. This should be worked like Cubical ([login to view URL]) and Picoston ([login to view URL]) At present we can control electrical equipment with our Wi-Fi Device (relay based) and two way switches, but we can’t control it using one way switch like the sited device. Even we don’t have dimming facility for all the devices. What will be the cost of the Wi-Fi device? What is our charges to design such device working like Cubical and Picoston? What time period you want to design it?