the seatbelt light is controlled by a switch in the buckle itself, on the side of the seat. you can find the 2-pin connector under the driver seat and unplug it, then short the connector with a piece of wire or something to fool it into thinking your seatbelt is actually buckled. on a gen4 camry this will not affect anything other than the bell sound when you first turn on the car (it won't ding at you), and the seatbelt light on the dash (it will be permanently off).
In my miata, the switch wasn't working right, so the buzzer and light were always going off... so i rewired some things and now the buzzer is a "you left your lights on" reminder sound. the seatbelt light never lights up anymore.
I do not need to be reminded to buckle up. seatbelts have saved me in the past, and so it's just automatic for me to put them on.