The folks over at TUAW are reporting that there is a DIY FM transmitter kit available. The MP3 Hi-Fi Stereo FM Transmitter. It says the circuit can be powered with any standard 9V DC / 50mA adapter. I wonder if a 9v battery would work. Any electrical geniuses out there know? The price is $39.95 with shipping of $7.45. There is also a Soldering Kit which includes a power supply for $34.20. Those prices seem a bit out of my price range to add it to my Shufflephones 2.0 The range is 100 feet which might explain the power consumption since it seems the iTrip would draw a whole lot less from the remote jack. I can see some definite hack potential here.
UPDATE: A faithful reader added: A 9v battery would work fine as it would easily be able to provide the current needed. Also, any regulated 9V mains adapter would power it fine.