Yes, you can do this just fine. By using a couple of resistors, you will prevent sending any data back to your RX from your TX:
Then, you will be able to use hardware serial like normal, including Serial.read() and Serial.write().
The resistors prevent TX and RX from pulling each other high and low, and instead let the remote end do it.
I use the same simple circuit to communicate with a hardware device that also uses a half-duplex, single-wire serial connection.
(Remember, you still need a common ground =)
EDIT: I forgot to mention, if you intend to hardware this connection, make sure to put a switch to break the COM connection, otherwise you won't be able to upload sketches.