Check out the video's for this transmitter/Watch. You can get this for $1.00. Only Downside is that it does NOT have a 3.5 MM jack. Instead it does have a mic. There is even a video demo of this. It actually keeps time too. Could be a fun transmitter to play with. An easy way when you shop for your Wife to find you too or for the Wife your husband. They could transmit and you trace the signal and as it gets stronger there they are. Neat.
http://pocketcalculatorshow.com/nerdwatch/casio-tm-100-transmitter-watc/