Is there any low level access to the androids wifi transmitter?
Obviously each android phone has a radio transmitter / receiver.
So how does one tell that transmitter to transmit say the letter "o" or the number 1 rather than a packet?
You will always send a packet, what you can change is the payload that, in your case, can be a string with only a "o" or a number. The packet is built according to the ISO/OSI stack http://en.wikipedia.org/wiki/OSI_model tho some levels are not always present.