This is a predator call I built using free apps available on Android, an 1/8th in. head phone cable running into a 9-volt amplifier. The amplifier output port would cause the speaker to bypass and put the juice into another 1/8" cable out with split leads going to a loudspeaker, split the wires between the positive and negative (doesn't matter much being mono though), sweat em together and get out in the woods/desert and use it. The setup cost about 60$ from radio shack and took maybe 2 hours to assemble.
