Buy a commercial product if you're trying to do an ipod transmitter, even the 'bug' you're using is going to have significantly higher output power than is legal. Seeing as how the output frequency shift is limited to the input voltage change the output could be easily overmodulted on accident especially while you're tweaking with component values. If you over or under modulate it badly enough the entire RF output section might oscilate and you could be creating harmonics and noise who knows on what frequency.