I turned ON a light from my android app , the light turns ON.
but the wall switch for that button remains OFF while the light is ON.
It's possible to wire a relay in parallel with the wall switch, and that creates an OR condition where either the switch or relay can turn the light on.
It's also possible to wire a SPDT relay and a SPDT switch as a "3-Way" switch (like where you have one switch at the top of the stairs and another switch at the bottom of the stairs, and sometimes up is on and sometimes up is off). The problem with that arrangement is that the software doesn't "know" if the light is on or off, so it doesn't know which way to switch the relay. It' possible to detect if the power is on or off and feed that back to the microcontroller, but probably not practical to do it that way.
But typically with home automation, the light switch is replaced by a special momentary switch/receiver so you have both manual control and automatic control, and the last command takes precedence. [u]Here[/u] are some switches that can be controlled by [u]X-10[/u] or other home automation protocols.
I don't know if there are any wall switches that can be directly controlled by bluetooth, but you can probably find a controller that accepts bluetooth commands and translates them to one of the more common home automation protocols. There are home automation controllers that work with Ethernet or Wi-Fi. Again, the switches themselves don't use Ethernet/Wi-Fi directly. The Ethernet/Wi-Fi signal goes to a home automation controller and the controller sends-out a signal to the switch.
I've got an X-10 timer/controller that's programmed via a serial connection from the computer. It can be directly controlled from the computer, but it normally runs as a stand-alone unit. This particular unit doesn't have any software for remote/network control, so I can't control it from a phone.